My 88 560sl did the same thing yesterday. I was driving on the highway and it started to lose power. I would stop the car and restart it, it would run fine for about 3 minbutes then lose poer again. After about 20 restarts I pulled the ovp and it ran fine. I had a spare ovp but the same problem was there when I installed it. It must have something to do with the fuel computer or idle control because that's the only fuel systems related to the ovp. Where is the fuel computer?