This may sound like a real stupid ? But i am new to this and also about 99% computer illiterate I just bot my 2nd 2nd generation Cummins (2001 Quad Cab 4wd) my first Cummins was a 96 It had a CAT. The 01 does not. Is this correct and legal for this truck? I am planning a 4inch exhaust upgrade but here in good old Mass. we always have to be on the lookout for the pollution police. Thank you for your help.