Have a 1995 gmc k1500 new dist cap rotor plugs wires fuel pump fuel filter have headers no o2 sensor no cat. When it is wet or slushy driving down the road it starts acting like its starving for fuel or losing spark then after awhile it clears up then starts again. Only does it when it is wet or slushy

 

Might try some silicon spray all over the cap and rotor. Also putting dielectric grease on the electrical connectors is always a good idea.

 

you can use wd40 to isolate the issue. i had a cracked cap once on my 94 it would act up if it was wet outside. i could spray the cap and the issue would go away. replaced the cap and no longer an issue. just a note the "WD" in wd-40 stands for water displacement