A buddy of mine is trying to get rid of his 420SEL (gas engine), which he says has terrible engine performance.... He says the pedal has to go to the floor before anything picks up, but once it's at full speed then it stays that way... He's been told it's a 'vacuum' issue, which I think is BS because I don't believe the vacuum has anything to do with the engine or transmission functioning other than performance/optimization/shifting/etc. He took it to a shop that supposedly got it to run on all 8 cylinders (how it was not running on all 8 I dunno), and came home with it in WORSE condition.

I'm looking at the car tomorrow to take it off his hands and I'm wondering if there's anything obvious to look at that could significantly affect performance/power? If it were a diesel, I'd consider something with the throttle (my 300TD had a broken throttle bushing that affected the power), or compression or maybe new injector tips). But I've yet to see the vehicle and aren't familiar with gas engine issues as much.

Any ideas?