check oil pressure, check to see if the throttle linkages may have been bumped,bent etc. Smaller filters should not have hurt anything. Maybe they started it dry then noticed no oil pressure, shut it down then added oil? This would of course cause some trouble.

__________________
1977 240D turbo

Your Quickie lube place is responsible for the damage unless you failed to inform them to the extent of your conversion... pardon if I misread. I skimmed..

Wouldn't be the first time i've heard of a quick oil change place doing this.....

__________________
1982 300GD Carmine Red (DB3535) Cabriolet Parting Out
1990 300SEL Smoke Silver (Parting out)
1991 350SDL Blackberry Metallic (481)

"The thing is Bob, its not that I'm lazy...its that I just don't care."