Mas or O2 problem

[prang11]

My brothers redtop is having some problems.

The car is having a hard time holding an idle. I expect this to either be because his MAS or his O2 sensor is fucked. The car will idle at 750rpm, once throtle is applied it will stutter then go no higher than 2500rpm. Obviously an ecu problem, code 55, 55 - Other Malfunction. CONSULT Terminal Required....

What we have tried: We put my AEM Uego on the car with a bung over 18" behind the turbo with the white wire (0-5 volt) hooked up to the stock O2 sensor read out wire. I always thought this could replace the stock O2 sensor, I may be wrong. The Idle came out at 15.3:1, seems a bit lean.

We replaced what we thought was a leaking injector but nothing changed. Maybe we need to have all 4 injectors rebuilt

The MAS is a stock KA24e and has worked fine before. This seems to be the only thing that has not been tested or changed.

The cars mods:
Stock redtop
3" elbow, DP, and exhaust
Front mount, ssqv
We have an safc not hooked up.

The car ran for a good 10 hours before any problems started. We put the elbow, DP, exhaust and intercoller on then had it tuned by unnatural. It ran fine for a few hours then problems started.

So MAS is my guess. Any other ideas??

Thanks guys.