I just spoke with a Sheriff here in town about this law... He waved me over to his car, I pulled up and to my suprise he said "Nice truck, is it strait piped?" I was honest about it and said yessir it is... He said as long as you have a turbo charger on it, it is as legal as can be. However any form of exhaust smoke MUST dicipate before 10 seconds. After that it is illegal. But he showed me the law in his little hand book and sure enough, The turbocharger falls under the muffler category. Just out of curiosity I brought up "hood stacks". They are not legal only because they do not exit behind the cab. Thats a law here in Texas. Now other states Idk. But I thought I'd mention that.