I have a 2003 Subaru Impreza WRX with a STI engine that I bought as is. Everything was fine until I washed engine it runs good until I push the pedle to the floor at any rpm. I believe its a boost leak or maybe a bad manual controller from what I have looked up. I just would like to know what would you all check first? I would greatly appreciate any help~
make sure all the vaccuum lines are tight. If that doesn't fix it do a leak test.
You also don't seem to know what's under your hood? Highly unlikely it's a complete STi engine. That would require new ECU, even new pedals (STi is drive by wire). This then makes it hard to give you advice on your boost control system because it's an unknown. Is it stock-like? 3-port BSC? MBC with ECU control? What?