Sorry to beat a dead horse here but I am new to Mercedes and just purchased an 04 E55 6wks ago and it ran good. Now it stumbles off the line and the supercharger works 10-20 % of the time. I did try the trans shift adaptation reset to see if would help but still runs the same. No error codes present at the time and from what I am reading everyone suggest replacing the aux pump. I am putting in the bosch 010 pump today and hopefully this works. Also whats everyones thoughts on the k&n drop in's ? Thanks group

 

Stumbling off the line is probably not a pump issue, but you should get the 010 anyway. Stock air filters are very good when new. K&N's let fine grit into your motor. You can see it build up in the throttle body snout inside the part that covers the rear SC bearings. I got rid of the filters when I had to replace the bearings. K&N's are great! Want to buy a used set?

 

Car actually came with them. Lol. But after installing the pump it does seem to run better but supercharger went from work 20 percent of the time to 50 percent. Going to remove it and check the engagement plate and bearing

 

The other issue with K&N's is that the oil tends to coat the MAF. People tend to put too much oil on them. In general, they're just not as popular anymore. I wouldn't run them, they can cause more problems and aren't worth any performance boost.