I have a 93 R1 that has engine built and tuned by SR Motorsports. It has the Apexi FC Commander and SR downpipe and Apexi catback. My problem is when at the dragstip(I race my brother in a WRX) if I take off fast and get the rpms up the second turbo will NOT kick on. If I take off slow and keep Rpms below 3000 and then hit 3rd gear and once past 4500 the second turbo will kick on but by that time my brother is gone I still have the stock cat, is it a back pressure problem? If im crusing down the freeway and hit the gas the 2nd turbo works great, its just the high rpm take offs. Any ideas?

 

Check this thread:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/turbo-problem-first-second-gear-only-tho-677318/