[87BOSS351C]

Did you check for bent valves??? If your engine managed to suck some water into the intake it may have bent a valve. Water doesn't compress so it tends to do nasty things to internal engine parts. Go to a parts store and get one of those fittings so you can hook an air compressor up to the spark plug hole. Loosen all of the rocker arms and see if each valve is sealing. If one is not (you'll hear the air leaking out), it is probably bent.