I recently had the front seals replaced on my 87 740 sedan. When I got the car back I noticed a vacuum leak on the air intake; stepping on the gas would not deliver a corresponding increase in revs or speed. I searched around and found a couple air-hose connections a little loose. This has improved the power boost at lower revs and lower speeds, but still, at a higher speed, when I step on the gas, the turbo gauge will jump to about 2 o'clock, but speed and revs will remain low. Of course there is rich, black exhaust as I'm increasing the gas input but not the combustion. I've cleaned the PCV box and flame arrestor. New air filter. Any other insights? I appreciate any responses and insights.

Tanks.
Shayne LaBudda