Hi, I have a 1990 GMC 383 stroker. Its idoling to fast. I have replaced the ICU, TPS O2 Sensor and the PVC valve and it doesn't appear to have any vacuum leaks anywhere. It runs fine it just idols to fast

 

Check to make sure your butterfly's in the TBI aren't hung up or the cable is holding them open more than they should be. There should be a little slack in the throttle cable. If all that checks out it has to be sucking air somewhere. I installed a throttle body adapter one time on a carb manifold and the adapter was causing the butterfly's to hang up. Just a couple ideas.