Just bought my second w124 30. My first is an 87 om603 that I bought for $500 and fell in love with.(installed a Keychain and have been driving it since)

My 90 2.5 turbo that I just bought is not cooperating however.

Car has 285k. Starts immediately with no smoke or hesitation.

Turbo is spinning at idle but is very quite, almost too quite. The 87 turbo sounds like a jet engine, not this one. Normal?

Car doesn't smoke if you floor it. Has torque to about 2k rpms then hits a wall. Will rev to redline but takes a scary amount of time to get there.

I've been stalking this forum for awhile but I'm still getting used to mercedes diesel jargon.

My guess is the turbo isn't boosting. I tried to move the wastegate by hand when it was off but I couldn't budge it.

I have an adapter coming to attach my boost gauge Wednesday but until then, any suggestions where to start?