I have a 1990 300SL with the 5 speed automatic. Similar engine and about the same vehicle weight. It's no rocket, especially if the AC is on. This engine doesn't produce much torque until about 3000 rpm's, then it pullls hard. I find the acceleration to be merely adaquate, but on the highway, theres plenty of passing power, especially with a downshift. You can get somewhat better acceleration if you hold back the shifts by manually upshifting the transmission. The engine revs easily and smoothly to redline. On the good side, it gets about 26 -27 mpg on the highway. My general driving average is low 20's. If you feel you need more power, you'll have to get the V8 and settle for poor mpgs.

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