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. Let me know if you find out and likewise.