Chevrolet Forum - Chevy Enthusiasts Forums - P0300 - What else is there to try?? HELP!!

Hey all,
I am posting for a friend of mine, i am working on his truck. he has an 03 silverado 1500 with a 4.3L V6 (if i should post this in the blazer forum, let me know lol). it throws a P0300 random misfire, misfire is continuous. it is driveable, but more than noticeable. engine light does blink sometimes, too. not much power at all. smells very rich, and reeks fuel out the tail pipe

things i have already checked/replaced:

- compression: all cylinders between 180 and 210psi
- fuel pressure: key on, goes up to almost 60psi, with engine running it stays around 55psi. i let it set for about 20hrs and it did drop to about 20psi in that time, but i cant see that being anything significant over 20hrs, to cause such a horrible misfire (its probably just my tool losing pressure lol)
- spark plugs, wires, cap, rotor, have all been replaced
- coil has been checked (with a new one that i will return lol)
- distributor has been checked (replaced with a new one as well, that i hopefully will get lucky and be able to return too lol) i was almost certain it was going to be the distributor, especially since there is that old bulletin for them concerning this code and condition
- checked for vacuum leaks, could not find any. on the manifolds or lines

is it possible that there is a computer issue? computer telling the injectors to stay open too long?

another thing, is that my buddy did say he washed the engine, and noticed it happening around that time after he washed it. i know that doesnt necessarily help, since it could still be anything lol. but there are no codes for any other sensors or anything.

any ideas, please help!!
thank you!!
Andrew