we installed an aftermarket boost gauge and boost controller and at15psi the car runs great but at 17psi it hits fuel cut.anyone know why?

 

It's the ECU doing that... all of them do. I'm pretty sure you can get it flashed or get a chip.

 

The reason your friends' car hits fuel cut @ 17psi is this: when the turbo is forcing ~400cfm of air into your motor, your 450cc injectors cannot compensate- even if they stay open 99% of the time, they cannot bring the A/F ratio back to 12:1.

Keep the boost down to about 15psi and you'll have no further problems. If your friend simply MUST crank the boost up to 17-20 psi, he MUST do work to his fuel system.

 

ok cool. i had a 95 with a big16g and never had a problem at 17psi but i know that some cars act differently than others. ill have him keep it low until he gets supporting mods.