SKIPS WHEN WARMED UP..baffled

[murf]

Have a 86.5 NA Supra with 35K on a rebuilt motor. It started to skip when damp so I put wires, cap, rotor and plugs in. Now it runs smooth on start up, but after several minutes (less than 5) will skip at idle. It also has no power under load. The skip seems to be #4. The car has 200k on it so I changed the fuel filter and fuel pump. I pulled the cold start plug while it was running smooth after start up....no change. I have had distrib pick-up coils build resistance with heat and act like this....so I changed out the distrib. Still no change. Again when it is first started it runs like a clock at idle..but will have a slight stumble when rev'd w/o a load. Any ideas??

Thanks