Alright, bear with me. I am not a Supra owner, but a good friend of mine just picked up a 89 Turbo Supra from Florida and drove it back to Texas. He is not to familar with the car nor am I, but I consider myself knowledged in general turbo systems, engine managment, combustion engines, etc. With that said, the car supposedly has a j-spec turbo motor swaped into it. It is also equipped with an aresenal of bolt-ons, including a Greddy Profec B boost controller. With the EBC off, the boost pressure peaks at ~5psi. With the EBC turned on, and as we begin to increase the boost, the ECU appears to be cutting fuel or ignition at ~6psiTurbo, as we "hit a wall" as soon as boost begin to exceed ~5-6psi. I am not 100% sure the "wall" is boost dependent, but from our experiementing it certainly seess so. What is manifold pressure regulated at on a stock 89 turbo? J-spec turbo motor? I am not aware of any piggyback electronics, but I will be checking things out soon. Just looking for some ideas on possible areas to look.