I have a 1996 S10 with the 2.2 liter. It's a multiport fuel injected 2 wheel drive. Parked it one night running fine. The next morning, it ran rough. If you hit about 2500 rpm (parked or driving) it begins to dog out (kind of like the old vapor lock problem). The spark plugs are quickly carbon fouled. There is fuel dripping from the exhaust pipe.

Here's what I've tried so far:
changed plugs & wires
changed coils
changed fuel filters
bypassed entire exhaust system
tested fuel pressure (within normal range, but doesn't drop 10psi at idle like the book says it should)
checked cylinder compression
changed fuel pressure regulator (used part)
checked vacuum system

Help! I'm running out of ideas!

Thanks,
Chris