Thanks for kicking some of the plaque loose on my Alzheimers. After you mentioned injectors a (dim) bulb came on, and I went out and looked at my service records. The tech that did the plug connector also told me I had a bad injector seal/sleeve. I had him do all the seal/sleeves at the same time. It was $81 parts and labor for the injector seals and sleeves, and $21 for the plug connector. 95% of the roughness gone.
For comparison, $400 at my tech was the cost of a complete 60,000 mile service including tune up with new plugs and filters, and trans/power steering fluid and filters, diff lubrication replacement, oil and filter change, lube of sunroof, doors, hood, adjustment of fuel mixture, etc etc etc. $400 to just to look at it is a rip! (IMHO)
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E