I just purchased a 2003 S2K and I have been having some problems while shifting. I do not know if it is me or if it is the car. Sometimes it will shake and studder while shifting between 1st and 2nd gears. I shift up btwn 3k and 4k rpms and down at 2k rpms. How can I tell if I am doing something wrong or if there is something wrong w. the car?

 

This statement would indicate to me that it's the driver. Shifting at such low rpms takes a little more finesse. You are most likely not matching revs very well. That is to say, your engine speed at the time the new gear is received is too far different from the what it needs to be for that gear.