When utilizing a new shop in my area recently the mechanic showed me that the wastegate valve on my 86 300SDL w/331k miles is stuck. The mechanic believes it's stuck in the "closed" position. Here's my question: What problems could I experience if I just leave the valve alone? The car runs great! I've put the last 231k miles on it myself. I can see that the valve is defintely stuck... but it's probably been that way since I purchased the car years ago. Under what conditions should I be experiencing problems? When it's cold, hot, under full throttle/load? How big is the job ($$$) to replace the valve? Does the exhaust manifold have to come off? The turbo? Thanks

The only time the wastegate operates is under max accel. There is a back-up called overboost protection, electrically it reduces power to engine by shutting off boost signal to fuel injection pump.