RB20DET swap running terrible, need help

[jwren]

I have an 1990 s13, i got it with an rb20det freshly rebuilt, pre-wired, etc. came with a "top secret" ECU. the maf is a little banged up. we got it together, and got it to run, but it runs terrible, won't hold an idle, you have to play with the throttle to get it to raise in RPM's. It will die if you just hold the throttle at a specific spot. What could be wrong? ANY suggestions would be very helpful, pulling my hair out over this. Thanks.