Check the dashpot operation:
- http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml#Dashpot

Should let the throttle slowly close instead of slamming shut. You can adjust the set screw to allow for more or less dashpot travel. I set mine to about 1/2 the plunger travel.

And you may want to re-check the TPS on the vehicle, I found mine changed a bit from setting it in the garage to when I hooked up all the throttle linkage and what not on the engine.