I have gteched my '86 300E consistantly at about 7.8-7.9 seconds 0-60 with 1/2 tank of gas and 1st gear start engaged. As for top speed, my car has no problem pulling up to redline which indicated to be just a touch over 140mph, probably 142 or so. I think it will vary a bit between years of the M103 though because I was told that my year had a little more aggressive cam then say the '91 which also has a worse tested 0-60. I think someone mentioned exaust as well but I'm not sure.

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-Kevin