If I understand correctly,, any modification done to your truck will make it *illegal*. Your truck comes with Federal certificates in all areas, in Safety (Airbags, Brakes, Suspension), Noise (Motor, Intake, Exhaust) Emissions (Fuel Pumps, Idle Speed, rated power), and many other things, including Lights, Blinkers, Door Locks, Lug Nuts, Shocks, everything in the truck is certified, any changes to your truck and it is no longer in exact compliance with federal laws.
So If your asking if it is illegal. Yes.
Will you get caught? Depends
Can you get a ticket? Yes
but in reality,, Do people care? Is the Government that strict? will the cop take time to give you a $100 faulty equipment ticket or a $300 speeding in a construction zone ticket?
The Government can't keep people from flying commercial jets into buildings,, Do you think they can stop you from removing your muffler?
My $. . 02 on the matter.
Merrick Cummings Jr