R129 - 1991 500SL stumbles after warm up

All, need your experience/expertise on this one.
I've researched all I can on this in the archives.
My car consistently does the following: When starting cold, it feels like it's not running on all cylinders.
Then after a second or two, the idle rpms come up, and the car runs fine. After a few minutes, the car will begin to stumble again. This has been intermittent for months. Now it is guaranteed to stumble intermittently for a bit, and then go to a clear performance loss, and vibration, like a cylinder has dropped out of the mix. This remains the case until the car has sat for hours.
In an effort to remedy this, I have replaced the spark plugs (7 were clean dry, and somewhat grey film, 1 had some carbon, but not loaded up, or fouled), distributor caps, and rotors. The car ran GREAT for about 24 hours, then back to the same old thing. (sat for 3 days waiting for parts)
I checked all plug wires (didn't remove them though) to make sure the cap ends were screwed on tight on both ends.
Now I'm starting to think that maybe the car has sludge in the gas tank, and doesn't get starved until it's been moved for a bit, and it's not really temp related.
Today, I'm going to start the car, and let it idle for a half an hour or so, to see if it starts to stumble.
more info. started the car, carefully backed it out of the garage, and let it sit running. After 20 minutes, went out, and it was consistently dropping and recovering rpms. Had a bit of freeze spray, and tried shooting both coils to cool them down. No change. tried shooting the fuel distributor (spider on the top of the engine). no change, but not much spray left.
I am now cooling the car down, and will try later to restart.
After the car cooled, I restarted, and it ran fine. Went for a ride, and within 5 minutes, it was back to missing again. turned it off, and restarted, still stumbling. So, maybe it IS temp related.
any other bright ideas?
TIA
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fuel starved?
change ALL FUEL filters. check again. if it still does the samething you may have doo doo in the tank OR the coils are breaking down because of under hood heat.
just guessing but i go for the cheaper way first!
case
the case, minus a few cans!
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Check the OVPs... or have them checked...
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snipped-for-privacy@aol.com (AJDalton7) wrote in message

OK, I give up. Overhead Valve P......? or something else?
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snipped-for-privacy@aol.com (AJDalton7) wrote in message

of course, I decided to search on ovp. Overvoltage Protection Relay. duh. I'll give em a look
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snipped-for-privacy@comcast.net (C. Sadler) wrote in message

Final follow up. It was exactly the plug wires and/or caps. Don't care which one.
245.00 for a complete set of Beru wires at speedycarparts.com and one pain in the rear to change out. These don't have removable caps, so that requires disassembling the races. If you have a tip on an easy way to do that, please post it.
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