Too long of a gear ratio with not enough power...All cars are different, especially when they are different makes and models. Gear ratio, weight, differential, low end, high end, tuning, clutch, TIRES...everything makes all those cars run differently. s2k for example is VERY light making very good power vs wieght making them a good adversary on the track, I just don't like convertables...sorry.
As for the noise, thats just how this transmission/drivetrian is. If you let it idle you can here chatter coming from the tranny. you could try using readline tranny fluid and that should help it run quieter:
Redline MT-90 1 qt (manual transmission fluid)
you can also try to change out the diff fluid also.