Stalling in the Rain
 

I have a 1990 Jetta GLI 16v with 250,000 mi. Needless to say, this has been a wonderful car except when it rains. Once I've run through a couple of puddles, the car begins to misfire, and eventually stalls. I've tried replacing spark plug wires, distributors, fuel pumps (both front and rear) but had no luck. Any suggestions would be greatly appreciated.