Truck Repair: 98 chevy truck hard morning starts, chevy truck, dry weather

Question
Hello Van ..98 chevy 1/2 ton 5.7 liter motor... dry weather starts hard when engine is cold..runs rough,hesitates at slow speeds until warmed up,nail it to the floor and seems to be fine....today first rainy day in a month.truck will not start. after ignition is released from start position it seems to fire but on wrong cyclinders maybe once or twice coughs up through throttle body... never starts. now heres what has been replaced , spark plugs and wires, distibutor cap and rotor. a friend of mine retrieved a code on a dry day when truck did run that it had misfired. check engine light did come on that morning but no sign of it since. Tried drying the distributor with hair dryer, no change.was thinking myabe a fuel pressure issue, but within the last 2 weeks pulled a trailer with 3 ton on it and it was fine up and down the steep hills. clogged fuel filter,temperture would not effect? have appointment with chevy dealer next week. would love to solve this on with out their help, with a labor cost of 80.00 an hour. you got any ideas that a back yard mechanic can go with this?

Answer
Hi Steve,
I would want to know the fuel pressure is good at the throttle body. Needs to be 13 PSI or so.
Then I would want to check for good spark.
Sounds like it could be the ignition switch not sending voltage in the start position, possibly to injectors or coil.
Have you tried priming the throttle body, or starting fluid? That would verify spark.

Timing is another possibility.

Van