Get rid of those accel plugs and go with some NGK's. The screw on terminals on those accels NEVER stay tight or contact worth a darn. Sounds like youre loading them up, and whatever mixutre you have to run with the way they work isnt liking you once its warm. Put in a heat range hotter NGK plug, and lean out the idle circuit a bit. It will be a tad bit more tempermental when cold, but will be a world different warm. Also toss in a backup distributor of any kind to confirm that your pickup isnt having a problem, or its not having a phasing problem etc.