124 runs rough after freeway runs

I had a problem that started today, after a freeway run I pull off the freeway up to the light and it's running as rough as can be, you'd swear it's a big vaccum leak. after about a mile or so of city driving it clears up and it's just as smooth as can be. Gas milage is good, temp. is fine. I did notice the smell of a hot cat. converter on a uphill run, I'm not positive it was me. By the time I get home everything is fine.
Any ideas, suggestions? Tomorrow I will get it up on the freeway and pull it over and look under the hood, see whats up.
Thanks for any input,
Chris C.
86' 300E
152,000 miles

[Benzmac]

I would have the engine put on an ignition scope for a possible faulty resistor tip problem.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Thanks Benzmac,
Well I put a reply to this a couple days ago but it didnt show up?
Anyway it was a vaccum leak the #1 intake runner has a vaccum hose fitting on it and the hose was just rotten, I replaced all 5/32 hoses. Now Benzmac what did you mean by resistor tips? Spark plugs? I was just wondering.
Thanks again,
Chris Campbell

[E. Lee]

Did you replace all the rubber joints as well? Or just the vacuum lines?

I'm planning to replace all my vacuum lines...but I don't know if I need to replace the rubber joints as well.

Let me know. Thanks.

resistor tips would be known also as the spark plug insulators that are on the end of the plug wires and snap onto the spark plug. quite common on all benz's and all cars. always check the basics!

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E.Lee,
I replaced all the rubber peices that connected to the plastic vaccum lines. 5/32 standard vaccum line fits nice and tight. I found that the vaccum line I used was quite a bit thicker than the stock molded vaccum hoses so making 90' bends was no problem. I noticed quite a few of the vaccum fittings were loose on there nipples. I also pulled apart and lubed all my throtle linkage at the same time. I don't think that has ever been done.
See ya,
Chris C.