Interesting. I know somewhat about maintaining proper velocity in the exhaust system. I had a 350 in a Surburban that I put dual 3 inch exhaust on a stock engine. Way too big! You could put your hand on the tailpipe after driving 100 miles in the summer. In the winter as soon as you got off the freeway the pipes would steam like when you first start out with a cold engine. The overall view here is that for a near stock 250 a single 2.5 inch pipe is about right or dual 2 inch pipes. I was thinking of either running twin 2 inch pipes for s certin distance into a 2.5 single or just starting out with the single 2.5 pipe. I just didn't know how much advantage the the twin head pipes would give. Thanks for the replies. Jay 6155
