I have a 1989 190E 2.6. The car hesitates a lot when I'm driving in the city. It runs fine when it finally opens up on the highway. When pushing down on the gas pedal it seems like I'm pushing air. The car losses a lot of power then pickups up again. The problem comes and goes. The biggest problem is when I'm entering the on-ramp of the highway the car won't go faster than 40 mph for a least one mile then it kicks in and is fine the rest on the ride on the highway until I get off then the hesitation starts again (intermittingly). One mechanic had me change the plugs, distributor cap, wiring, and air flow meter. The dealer couldn't find the problem. They had the car for two weeks. They said they test the fuel pressure, back pressure and that the O2 sensor and coolant sensor were borderline, but believed to be okay. Any help would be appreciated!!