I checked my back pressure as I have been doing for 20 years and the system checked good. I hold the rpm at 3k and it should read under 1.5 lbs. I found with the turbo system that formula does not work well. I drove my fd with a gage in the 02 sensor port and pushed a midrange ammount of boost and the gage read about 4 psi. I removed the cat and it was busted up inside and restricted. I am thinking the small size of the engine (CC) and a large volume exhaust the cat will check out good using the typical 3k test. Has anyone tested their systems and have some more numbers to share.

 

I've been watching for posts on this same subject. Here's a thread on my test results.

https://www.rx7club.com/showthread.p...t=backpressure