I had two burned exhaust valves in my 90 850 Turbo at 51K miles. Had it fixed at the dealer because Volvo agreed to pay half the $1,500 charge since it was barely out of warranty. So you could possibly get it done for less at a good INDY. I have had no further problems with 102k on the car and absolutely love it.

BTW, no one could figure out why the burned valves, but the INDY that I go to now (when I can't or won't DIY repairs) says that he has seen a number of problems with 850 engines and Bosch Platinum plugs which is what I had in the car at the time of the problem. Use only Bosch Super copper cores now...