My 95 with a 5.8 will act like its running out of gas when we get a all day rain,the problem is it will not last long enough to diagnose. It will run fine on the initial fire up but after the motor is warm and I shut it off then it starts to act up but just for a few minutes then it goes away,it smells lean so what ever it is its causing a lack of fuel to the motor so where does one start to look and its not turning on the CEL.

 

Check the seal between the cowl panel and the hood. Sometimes that can deteriorate and corrupt the MAP sensor on the firewall. Otherwise check your grounds and connections.