I've been having a problem lately with trying to start my truck in the mornings, especially on rainy days. Its a 94 F-150 with a 5.8L

It sounded more like when the distributor cap gets moister inside so I decided to change it and the rotor since I havent done that for awhile. Well all was ok for about a week, but today it started to do the same thing again. I was planning on doing the plugs and wires next. Only thing is I dont want to end up spending a fortune trying to figure this out if the plaugs and wires dont do the trick.

Any ideas on what else I could look at would be appreciated