380SL Misfiring/ Loping idle?

[ArborWrench]

1982 380SL and I suddenly have an issue with what I think is a misfire. I can't pin it down to just one cylinder though. It's kind of loping when at idle and I held the revs at 3000 and it does the same thing. The engine idles normal then rev dip then back go up very quickly and it cycles through this quickly.

I just redid the heads a couple hundred miles ago and replaced all the vacuum lines and it was running like it was new. This developed all the sudden a week ago. I've put new plugs in, new wires, cleaned the rotor and dist. cap and replaced the coil. I'm going to swap and old dist cap and rotor to see if that makes a difference.

I've checked all the vacuum lines and they are all still tight. At this point other than swapping the rotor and dist cap I'm running out of ideas. I wonder if it could be a clogged fuel injector or bad fuel? I put some cleaner in just in case but that hasn't made an effect yet. If the cap does't change anything I'm going to run through the troubleshooting section of the injector controller and see if that could be the issue.

Any thoughts or ideas is much appreciated.