truck won't stop skipping

I have a 96 chevy S-10 that has been skipping for almost 5 months now. when it skips it feels almost like a cyclinder isn't firing until I get high rpm's in each gear and it skips in gears 1-4 and very seldom 5th gear. after the truck gets good and hot about 90% of the time it will run like a new dime for the rest of the day. it also will run fine as long as you drive it everyday, until today. I've put new spark plugs, new plug wires, crankshaft sensor, throttle pos. sensor, 2 coil packs, new ignition module, and loaded the tank with Seafoam fuel treatment and regular STP water treatment and fuel injector cleaner treatment. Does anyone have any clue what else there is to try or ever had this problem before?? I've heard it can be the MAP sensor or the computer but we've tested the computer and it's fine. Any help will do. thx all