I tried posting this in the 2nd gen specific section but didnt get much input. I'm thinking it may be a tuning issue as I removed the BAC and adjusted the fuel pressure.

Quick background. Just installed new street ported s5 turbo motor to replace the one I blew last year. Car ran old motor for 5 years at over 400hp, everything worked well.

Running PFC, adjusted FPR a bit down to 40psi idle (from 44), just removed BAC valve, OMP, and blocked off coolant to Throttle body. Otherwise, turbo, piping, etc is all aftermarket.


Problem/Symptoms:
Car fires up fine and revs to 2000rpm on its own. Sounds smooth. After about 5 seconds its cuts out and tries to stall, I can catch it with throttle and hold it around 2500rpm for another 5 seconds or so but it will again cut out, even with the throttle still held at 2500. This cycle might continue a few times or it'll just drop too low and die.

The BAC was recently removed, but I always had the air input blocked off, so not sure if that's is the issue.

TPS was never touched.

Any thoughts? Anyone had a similar problem?
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When you do not run the stock system to control idle air, you need to change the PFC settings for manual mode. This has the advantage of now allowing you to actually change the timing for the idle area of the map and forces the PFC to actually use that timing.

Set O2 FB and Idle Cntl switches off. Set the three idle speeds to 0.
You now have to physically open the throttle enough to get enough air for idle. And you also have to adjust the fuel for the idle area.
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Some FD single conversions will run the ISC fine and some will not. A problem not yet solved. So we single FD owners sometimes are forced to run what I describe. I have been doing it since 2004.