Quote Originally Posted by Casey_SS View Post
Just remembered another LT1 nugget - the coolant temp sensor in the water pump is used as a critical input for fuel & timing calculations. Both the sensor itself and the pigtail it plugs into have been known to go bad and cause issues like this.
Ford's, in my experience, have the same issue. Additionally, a failed/bad/malfunctioning ACT will cause all sorts of drama. Whenever I get certain symptoms that point to a failed ECT, I'll replace the ECT and ACT, just because. They're cheap, and easy to replace.

Check plugs and plug wires (remember when you're original motor was down on power, oh so many moons ago?), and the O2's as already mentioned.