i have a 93 i still have the stock twin turbo set up, with minor bolt on upgrades. i just put a new engine in but was having this same problem before anyways. when the car is cold everything works great and she hauls. however. after it warms up and i punch it i watch the boost guage go up to around 10psi and then drop right off to about 2. it sounds just like the blow off valve is just opening and letting everything out, so i rebuilt mine, same thing, so i got a new one, same thing. so i know that it is not the blow off valve. im thinking probably waste gate? if anyone has any ideas, or has run into the same problem i could realy use some advice. i am a 3rd year auto apprentice, so i understand all the technical stuff, but turbos are a little of a weak point. hopefully not much longer.

Thanks.

 

have the original plastic cross-pipe? It can crack and cause a glitch to open when car is hot.
Same with the original plastic pipe coming from one of the turboes.
Plastic tanks on the oem IC can fail.

WG can be tested if you have a airtool and a vacuum/airpressure-tool to recreate conditions actuators work under, like the wg-clock. If you have the opportunity, connect onto the WG for ex, and see if the arm is
1.moving
2. holding vacuum/keeping pressure

 

Read through this thread https://www.rx7club.com/3rd-generation-specific-1993-2002-16/how-test-your-solenoids-actuators-other-turbo-stuff-802060/

There are also a few links to good troubleshooting info on other sites in the faq sticky.