93 300D, 2.5T W124 diesel.

History: I've had this car for 5 yrs and 75K. It never has seemed to have the advertized power that I read on here (0-60 in 12.8secs). Ok, fine, it's a 20 year old car but my 0-60 is probably 30 secs. Finally, recently I totally lost all power, engine idles and takes off just fine but had no boost (boost guage installed awhile ago, turbo had been working as the OEM set up, vacuum wastegate style). Always felt like maybe not enough fuel. Then a couple weeks back, no boost, no power just a real dog worse than it ever has been. Never sounded like it was going to die, just a dog. I could only get 62 mph up hill on the freeway locally (modest grade here in central NC). Runs like mad on the level or downhill of course.

So, I did the gsxr wastegate mod, switched over to the pressure wastegate, boost on default set up. I now have boost, up to ~13 psi at max RPM's but still major lack of power. Car has zero smoke under hard acceleration.

Fuel filters changed, no change in performance. So I gave up and took to the local MB shop (ABW in Chapel Hill, NC). I told them when i dropped it off the mod i had done to the turbo.

Oh boy, I get a call today from a mechanic (had a bit of an attitude) saying all my vac lines are buggered up and I can pay him $95 and hour to hook back up. I say no, no, no, you don't understand. So I try to explain this is now like the W123 style. He still doesn't follow me. Says I have no boost to trigger the aneroid sensor (I assume that is the alda??). I mention, look at the boost gauge on the dash, it should say around 12 psi when winding up! Then says my vac is bad, well I have one of those gauges too, reading 22 mm hg. At this point I am thinking uh oh, I am in trouble with this guy. He says he blocked the EGR port and no change (well duh, that is unhooked now that Ihave the pressure wastegate set up. I just left the vac line there for looks for inspection. I guess he never noticed the other end is off, just there for looks for the NC stateinspection).

So I told him - just stop what he's doing. Please don't work further on my car.

So I am on my own (and this forum). Now what, please help!!! I am looking for what to do next for diagnosis to find my problem. I really feel it's a fuel supply issue. When i changed the filters, fuel just ran out of the supply line freely, didn't seem plugged but not sure what it should look like. things on my mind are the following.

Do the ALDA's screw up ever?? How do I tell?
Does the lift pump ever fail?
Anywhere else to look and how to check things out.
I've done some searching here but not exactly clear on how to proceed. I am a moderate DIYer and can usually think through things but want some advice from the guru's here. Thanks!