Tony,

I thought of that.  Perhaps if you run leaner than stoich on boost it may trigger a code or even limit load.  I can't see it doing anything to fuel as it won't know how much.  It isn't closed loop, and you would need a pretty major fault for it to actually matter.

Rick

Ok, how ECU will see that you run "leaner than stoich on boost" then ? From primary O2 sensor(s) right ? If thats not closed loop then what is the difference ?

And are you know exactly when ECU try to limit load emergency and how ? Are you ever had such situations ?

well my upgraded pump from 034 showed up today and I got it installed.

Slowly started increasing boost while logging.......and managed to hit the area I was having trouble with........and then exceed it without running lean as hell.

So it turns out my suspicions (which I were hoping weren't true for my wallet's sake) were actually true.  The car is running like an animal in this cool spring weather.

Thank you to everyone who offered suggestions and input.

This is a very interesting topic. I had to deal with a 225 hp TT (with a gt2871) recently that after being tuned a year ago (by us and another company) began to slowly start to run very rich (10:1 and more) flatlining our wideband 02 we use on the dyno. It is a narrowband ecu. Unfortunately the customer lives a couple of states away, and I only had one solid day with the car (in addition to running the business) and a couple of hours the next morning. It would only go very rich at wot and above 5500-5700 k. He made no changes to the car over the period of time since it was on our dyno and when it came back other than a higher flowing fuel pump. I tried to help him out remotely based solely on his description of the problem and a few low sampling rate logs. When the car arrived we tested/logged everything we could think of and everything checked out, but the car would always run so rich to the point it would hesitate really bad in the upper revs. The car put on 3-5k miles in between with it running great when it left, and for his first few all day race events (plus being driven home 3 states away). We logged fuel pressure, ran it mafless, swapped mafs, swapped 02's in a brute force attempt to resolve the issue because of the time crunch. It would do this at 15 psi and at 25 psi. Sorry to post jack, but I had my suspicions of it being a hardware fault, and was told by our software tuner the ecu ignored 02 feedback at wot, so this couldn't possibly be the case..I guess this should be in another thread altogether?