Ignition Problem

I have a 92 Camry with the 3vzfe V6, 182k miles.

Recently it has been having a problem where it wouldn't start when it was rainy out. I looked at the distributor, and saw that it was visibly sparking. On a dry day, I started it, poured water on the area, and the car died. I lived with this problem until last week, when I was driving home. Usually it was only a problem when I tried to start the car, it would start very hard, but then be fine.

After the first snow storm we had, I was driving home, nothing out of the ordinary. I parked my car. THe next morning, and ever since, it seems like it has been misfiring on 1 cylender.

I had the mechanics replace the cap&rotor, as well as all 6 spark plugs. The problem is different now... but still seems about the same. The car, warm, cold, wet, dry will misfire (not fire at all). At idle its usually decent.. ~50% of the time its hitting on all cylenders. You'll hear it miss here and there. When your going up a hill at ~50 (4th gear, ~2k rpms) it shakes alot. At other times, it seems to be ok, and misfire sometimes, but not all the time. It definately seems to have a pattern to it.. but I cant figure out why. The mechanics said they ran a test where they would drop a plug off, and watch the RPMS drop trying to find the bad one... and none of them seemed to drop the RPMS worse than any others.

I have the typical valve guide leaks going on.. but not major.

Any ideas whats going on here?