I have a 97 Z/28, I replaced the stock muffler with a flowmaster when it burned out i went with the Flowmaster cat back system and believe it or not it slowed the car down 4 Tenths in the 1/8 mile. Could someone tell me the stock size Dia of the pipe that runs from the cat to the muffler and the stock size Dia of the tailpipes i am thinking that the pipes that came with the Cat Back System are to large in Dia this is a Stock Z/28. And the MPH didnt change it was the 60ft time that changed. Thanks

 

The stock intermediate pipe on my 94 was 2.75".
Just so you know, it's your trap speed that shows the power your making. So if you didn't lose any speed than you didn't lose any power.

 

You can kill Torque and still have the same MPH.