Engine misfire? Can you help me fix it?

I noticed car idling rough and jerking on acceleration. Mechanic said water in gas. Tried bottle of heet; didn't work, check engine light came on; code read misfire #3; mechanic replaced plugs, wires, upper intake gasket; used some fuel injector cleaner; cleaned throttle plate. A little better but stlll when slow down and then accelerate back up it chugs; runs smooth otherwise except same day we got it out of shop check engine light came back on. Took it back to mechanic--he says fuel injectors need cleaning which will cost another $300. I hate to keep throwing money at it trying to find what's wrong--but I'll need to get it through emissions in a few months- Help please!

I have a 2002 Ford Taurus with the 3.0L OHV engine. I have been experiencing a missfire ever since purchasing the car. I have replaced so many components I'm down to a valvetrain issue. I just did a running compression on two of my cylinders and both were not even reaching 30 psi. When I revved the engine the compression dropped way down to barely being registered on the gauge. Is this evidence of weak valve springs or no? Also, the CEL is not being illuminated but the Mode6 data from my PCM indicates a small misfire on all cylinders (the last time I checked it).

I did a dry compression test several months ago and everything checked out. All cylinders were within 15 psi of each other. The running of the vehicle hasn't changed since then I just decided to finally take a stab at checking the running compression. I can do a wet compression but it would be this weekend before I could do it.