So my dad is coming out next weekend for the holiday, and since he only comes about once every 2-3 years, I really wanted to be able to take him for a go-kart ride. However, I'm needing some help getting the car back to running again, I'm not sure what I've screwed up because it was running fine, and now it won't run at all once it warms up unless you keep your foot on the gas.

It seems like this started when I put the exhaust on, but since I haven't been driving the car much, I'm not positive. I did have some problems with it running rough a few months ago, and cleaning the MAF appeared to have cleared that up.

What I've do so far:

Since the car is DBW, it has an idea re-learn routine you can go through, I did that this morning. The car started off rough and then smoothed out until it got to 180, and then it stalled and won’t restart until it cools off.

The MAF seems to be working, I can blow a fan up into the intake and it will increase in voltage (as read by the ECU and reported through ROMRAIDER). It reads about 1.3v at idle, jumps to 1.8 if I blow air up in there.

The O2 sensor is brand new. Lambda starts at 1.0 when cold, then once it has warmed up (about 120 engine temp, but its probably based on sensor temp) it drops to 0.76 and just stays locked on there. Once it was solidly locked and not moving, I used a propane bottle to blow some propane in the intake, and the O2 jumped up to 0.82, and then started moving around until it closed in on 0.95. I think the O2 is working based on this, but I'm not positive. I'm not sure if the fact it moved off of 0.76 and started working towards 1 was related to me blowing propane in there, or just coninciden based on temperature map and moving from open loop to closed loop.

Could my map be that far off after adding exhaust, or could be a sensor issue? Knock count is 0 on all 4 cylinders, even when running rough.

Thanks guys.