Is exhaust pipe measured by its OD like tubing or by ID like pipe ? I cant remember ? I'm wondering because I have some 2" light wall stainless pipe laying around and I was thinking about hot bending it up for a new exhaust pipe. or should I get 2.25" pipe instead, will a 1/4 inch really make a hole lot of difrents in flow ? I don't have a header and I will be taking out my cat since it is at its end of its life, and I don't have the cash to replace it right now, So what is better 2" or 2.25" pipe ?