Help Please Help!!!!

I have a 99 mkIII Jetta Wolfsburg with a 2.0L unmodified engine. When the car reaches full operating temperature, it stalls and will restart, and if run above 3,000 RPM will run very smooth but then cut off as if someone has shutoff the ignition within a few seconds. The car cannot be restarted by popping the clutch. The car runs perfect when cold.

I've recently done some tune-up work that may or may not be related:
New timing belt
New plug wires
New distributor cap and button

I have done this kind of work before and had the help of a friend that is a good mechanic. Both of us are stumped. I'm ready to take it to the dealership and get an answer but, thought I'd ask here before towing it and paying loads of $$$ for something that I may be able to do myself.

Our guesses are:
Throttle position sensor
Temp sensor
Other sensor?

Thanks a million if you've experienced this and know the answer.
No Codes No nothing in the computer

thx in advance

Guess it's time to crack out the DMM and check the sensors...
Are you sure you set the timing correct when you replaced the timing belt?