The fact that you have a "global" fuel delivery problem points to fuel enrichment or turbocharger issues.

When you romp on it with the ALDA turned out, do you leave a massive black cloud? If so, the turbo is probably on its way out or in need of rebuild.

If it doesn't churn out a Chernobyl cloud, the fuel isn't being enriched. You could have air ingress, ALDA line issues (if the ALDA is hooked up, it's still doing something), weak lift pump, improper timing, a weak/broken timing device, or even a linkage issue.

If you have a hand vacuum pump, try pulling vacuum on your ALDA. If it doesn't hold or if you can't build vacuum, reseal it with new O-rings. If it does, take it off the engine and make sure the plunger it works on is free to move. There have been a couple of folks post on here that theirs were seized up. Check your linkages for the correct lengths and make sure that pressing the pedal to the floor causes the IP linkage to move to its stop.

Lastly - put that clear line in place of the return line and look for air.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)