I searched first and could not find.

We have a 2.0 ABA with 1.8 head with Digifant II FI.

The engine will start fine from cold.  As it warms up it will stumble on throttle.  Press throttle open - Baaaaaaaaah - nothing.  Lift throttle, returns to idle, sputters a bit like it’s missing, but then continues to idle fine at normal speed.  Crack throttle open gradually and it may catch the first time, but then baaaaah, until you lift.  The hotter the engine, the worse it is.

I’ve found no vacuum leaks in intake.  Unplugging O2 sensor makes no difference ( a new sensor is on the way just in case).  Unplugging Temp sensor only raises idle slightly, but no difference.  I changed fuel pump and fuel filter with my new spares, no difference.  I swapped AFM, no difference. Spark Plugs are recent.

My son mentioned some stumbling issues when it was raining hard, and current issue appeared after he filled up with gas.  I added gas dryer, but no difference.

Ideas?

Chris in atnaltA.