I completely understand about the Jump. Mercedes is famous for poor acceleration. You have to roll on the throttle, you can't just grip it and rip it, if you will. The other thing that you might be able to look into... You might want to check your intake manifold. If you have a real poor idle, and seems like it could be diving in the RPMS. You may have a bad one. The SLK, & CLK classes apparently have a 50/50 chance unfortunately. I guess they have a high rate of failure.