1989 560SL runs rough until re-start
 

I have a beautiful 1989 560SL in my shop right now that has me a little puzzled. When I got it, the car ran rough intermittently and it had the CEL on. The led flashed 4 times for me, so I replaced the air flow meter pot with a known good used one, and the problem seemed to have gone away, and I believe the car ran much better, even compared to when it was not having one of its fits. Today about 30 miles since I replaced the air flow, it acted up on me again when exiting the freeway. It seems to continue to act up until I shut the car off, and then re-started it. It feels like its running on 7 cyl or less. It does not die on me, but it struggles to go 25 mph. I was able to check the car out at my shop, while it was acting up, and I verified that it had spark to all the plugs.

Any thoughts?