Actually.... I was just reminded of a problem I ran into some time ago with my best friends WRX. We had installed one of the early Vishnu Stage 1 setups, and I was wiring in a "unichip." (anyone remember when those were the thing to have? ). Well it turned out that I made a very simple mistake when reading the wiring diagram and ended up cutting the TPS lead into the ECU instead of just tapping into like I should have. I didn't notice it right away and we started driving the car. Well...the car of course was behaving like it was possesed, with all types of throttle surging and hesitations. It was terrible. The next day (when I wasn't so tired anymore) I went over the diagram and looked at my wiring and of course immediately saw the problem. Fixed the wires and 10 minutes later the car was driving great.

Lesson: Never underestimate the difficulties that can be caused by simple wiring problems....