[tubbedII]

Hey dads...did you ever get a fix to this issue? It's been a while since the OP.

Well, I'm not 100% sure on the difference between a '96 and a '01 (which is what I have for a DD), but there's a spider injection set up under the top half of the intake manifold on my '01. There's little plastic tubes that fail over time and usually is where the bleed down comes from. It's either that or the fuel pressure regulator which is also connected to this whole injection set up. When mine failed, it acted just as you are saying.

The "easiest" way to tell if this is the case was to pull the throttle body off and see if you have wash down on the back side the lower intake manifold. It should be pretty black, but if there's been gas leaking from these tubes, it usually washes to the back and leaves a nice looking aluminum.

If this is the problem, GM makes a newer part that's around 150 or so that replaces all the injectors with a better design as well as the regulator.