Car will run fine when it's first started but after it is warmed up it won't go above approx 1,900rpm without immediately shutting off. Once the rpm drops back down close to idle the engine will refire.

It's almost as if the fuel cut point has suddenly been set very low with an even lower engine restart rpm.

Engine is a Turbo B18B with a GM 3 bar map using Uberdata as engine management.

I've tried reflashing the EPROM (however I didn't change any settings) and even swapped ECU's. I also tried swapping distributors with another known working unit.

Any ideas?