I took a look at the fuel bypass spring on the '83 617. It was at 20 mm. I stretched it out to 27mm and reinstalled. As I pumped the hand fuel pump to bleed the air it seemed to pressurize a lot more than before after a few strokes.

Test drove the car at 45 mph, then 60-65. It seemed to have only slightly more power.

It was easy enough to do, just have 14mm and 17mm wrenches to do the 15 min job.

__________________
.
1st MBz: 1982 300SD
2nd MBz: 1987 300SDL
3rd MBz: 1995 S420
4th MBz: 1987 190DT
5th MBz: 1984 300SD w/1983 300DT engine
6th MBz: 1999 C230k I'm 3rd owner, got it w/57,235 miles.
and manages Mom's 2007 R320 CDI