It's a 03 swap, and it sometimes starts right up, sometimes not, from cold I have to pat the gas for it to run, or it spudders and trys to die, then it will hold a high idle, but touching the throttle even a little causes a stall, it won't rev at all, EXCEPT once! I unplugged the map and it ran good. I shut it off and it won't run again well.

 

I understand you should reset ecu, but It can't really properly work, since it won't start and run unless I pump the throttle.

 

I tried changing the direction of maf, it didn't change anything, and all my hoses are firm, no leaks.

Does the 03 WRX have the e-throttle or is it cable actuated?

 

Are any codes stored in the ECU?

 

What is the motor swapped into and how was the wiring setup?  Were the wiring harnesses merged or was a separate harness ran for the engine, ECU, and associated sensors?

problem fixed! The map was improperly hooked up

Ok, glad you figured it out.