91 na engine misfire after warm?

101,000 miles! Auto trans. So this car has been bugging me for a month now. When cold it starts and runs fine. After it has warmed up and the car comes to a stop and idles it randomly misfires and chugs here and there. The car runs perfect otherwise and has lots of pickup. NO CHECK ENGINE LIGHT.
Things replaced so far:
Plugs
Wires
Cap, rotor (they were shot, looked original)
Valve cover gasket (was leaking and messed up plugs/wires)
Full bg fuel system cleaning- intake, throttle body, injectors pressure cleaned, addative in gas tank
Fuel pressure is to specs
Timing belt has been changed at 60k
No vacuum leaks that I could find. The little thermo vacuum switching valve on the thermostat housing had one of the vacuum ports from the throttle body snapped off and was epoxy'd back on and thats the only thing I could think of that would be causing this issue. Any suggestions?

hmm, buy a set of NGK3330's and check your plug gap before putting them in. If that still doesn't work, run a diagnostic tool, no check engine light doesn't always mean that it isn't throwing a code.

check yur radiator for calcium deposites.