Attention: TDR Forum Junkies 
This is the Magnuson-Moss Warranty Act and was taken directly from Title 15, Section 2302, United States Code... Please note the bolded & underlined areas...
The Magnuson-Moss Warranty Act states, in part, in Title 15, United States Code, Section 2302, subdivision (c):
No warrantor of a consumer product may condition his written or implied warranty of such product on the consumer's using, in connection with such product, any article or service (other than article or service provided without charge under the terms of the warranty) which is identified by brand, trade, or corporate name; except that the prohibition of this subsection may be waived by the [Federal Trade] Commission if —
(1) the warrantor satisfies the Commission that the warranted product will function properly only if the article or service so identified is used in connection with the warranted product, and
(2) the Commission finds that such a waiver is in the public interest. The Commission shall identify in the Federal Register, and permit public comment on, all applications for waiver of the prohibition of this subsection, and shall publish in the Federal Register its disposition of any such application, including the reasons therefore.
Under this federal statute, a manufacturer who issues a warranty on your motor vehicle is prohibited from requiring you to use a service or maintenance item, unless such item is provided, free of charge, under your warranty or unless the Federal Trade Commission (FTC) waives this prohibition against the manufacturer.
Further, under the act, aftermarket equipment that improves performance does not automatically void a vehicle manufacturer's original warranty, unless the warranty clearly states the addition of aftermarket equipment automatically voids your vehicle's warranty, or if it can be proven that the aftermarket device is the direct cause of the failure.
Specifically, the rules and regulations adopted by the FTC to govern the interpretation and enforcement of the Magnuson-Moss Warranty Act are set forth in the Code of Federal Regulations, Title 16 - Commercial Practices, Chapter I - Federal Trade Commission, Subchapter G - Rules, Regulations, Statements and Interpretations under the Magnuson-Moss Warranty Act, Part 700 - Interpretations under the Magnuson-Moss Warranty Act. Contained within these rules and regulations is Section 700. 10, which states:
No warrantor may condition the continued validity of a warranty on the use of only authorized repair service and/or authorized replacement parts for non-warranty service and maintenance. For example, provisions such as, "This warranty is void if service is performed by anyone other than an authorized 'ABC' dealer and all replacement parts must be genuine 'ABC' parts," and the like, are prohibited where the service or parts are not covered by the warranty. These provisions violate the Act in two ways. First, they violate the section 102(c) ban against tying arrangements. Second, such provisions are deceptive under section 110 of the Act, because a warrantor cannot, as a matter of law, avoid liability under a written warranty where a defect is unrelated to the use by a consumer of "unauthorized" articles or service. This does not preclude a warrantor from expressly excluding liability for defects or damage caused by such "unauthorized" articles or service; nor does it preclude the warrantor from denying liability where the warrantor can demonstrate that the defect or damage was so caused.
Under the Magnuson-Moss Act, a dealer must prove, not just vocalize, that aftermarket equipment caused the need for repairs before it can deny warranty coverage. If the dealer cannot prove such a claim — or it proffers a questionable explanation — it is your legal right to demand compliance with the warranty. The Federal Trade Commission administers the Magnuson-Moss Act and monitors compliance with warranty law.
The Magnuson-Moss Warranty Act states, in part, in Title 15, United States Code, Section 2302, subdivision (c):
No warrantor of a consumer product may condition his written or implied warranty of such product on the consumer's using, in connection with such product, any article or service (other than article or service provided without charge under the terms of the warranty) which is identified by brand, trade, or corporate name; except that the prohibition of this subsection may be waived by the [Federal Trade] Commission if —
(1) the warrantor satisfies the Commission that the warranted product will function properly only if the article or service so identified is used in connection with the warranted product, and
(2) the Commission finds that such a waiver is in the public interest. The Commission shall identify in the Federal Register, and permit public comment on, all applications for waiver of the prohibition of this subsection, and shall publish in the Federal Register its disposition of any such application, including the reasons therefore.
Under this federal statute, a manufacturer who issues a warranty on your motor vehicle is prohibited from requiring you to use a service or maintenance item, unless such item is provided, free of charge, under your warranty or unless the Federal Trade Commission (FTC) waives this prohibition against the manufacturer.
Further, under the act, aftermarket equipment that improves performance does not automatically void a vehicle manufacturer's original warranty, unless the warranty clearly states the addition of aftermarket equipment automatically voids your vehicle's warranty, or if it can be proven that the aftermarket device is the direct cause of the failure.
Specifically, the rules and regulations adopted by the FTC to govern the interpretation and enforcement of the Magnuson-Moss Warranty Act are set forth in the Code of Federal Regulations, Title 16 - Commercial Practices, Chapter I - Federal Trade Commission, Subchapter G - Rules, Regulations, Statements and Interpretations under the Magnuson-Moss Warranty Act, Part 700 - Interpretations under the Magnuson-Moss Warranty Act. Contained within these rules and regulations is Section 700. 10, which states:
No warrantor may condition the continued validity of a warranty on the use of only authorized repair service and/or authorized replacement parts for non-warranty service and maintenance. For example, provisions such as, "This warranty is void if service is performed by anyone other than an authorized 'ABC' dealer and all replacement parts must be genuine 'ABC' parts," and the like, are prohibited where the service or parts are not covered by the warranty. These provisions violate the Act in two ways. First, they violate the section 102(c) ban against tying arrangements. Second, such provisions are deceptive under section 110 of the Act, because a warrantor cannot, as a matter of law, avoid liability under a written warranty where a defect is unrelated to the use by a consumer of "unauthorized" articles or service. This does not preclude a warrantor from expressly excluding liability for defects or damage caused by such "unauthorized" articles or service; nor does it preclude the warrantor from denying liability where the warrantor can demonstrate that the defect or damage was so caused.
Under the Magnuson-Moss Act, a dealer must prove, not just vocalize, that aftermarket equipment caused the need for repairs before it can deny warranty coverage. If the dealer cannot prove such a claim — or it proffers a questionable explanation — it is your legal right to demand compliance with the warranty. The Federal Trade Commission administers the Magnuson-Moss Act and monitors compliance with warranty law.
