| The sl is not a pure racecar. The 600 is made for people who want lot's of 'smooth' power & still have a lot of comfort. It is normal for an automatic transmission that it will move the car on idle, this is exactly done to make it smooth, it is meant not to snap when floored.
If U want to make it a racer then U should modify a lot about it, strip it completely down, only use components that a race car needs, remove electronics, replace/remove heavy stuff, add wings, lighter manual transmission and so on...
IMHO this is a bad idea, all the adbove will help but U will never get the real race performance out of it because of aerodynamics and weight.
Sure it'll be fast in straights but it's just too heavy to take fast corners like a real racecar.
Also most people will find it difficult to drive cause of the bumpy behaviour which is very tiresome so it will be very difficult to re-sell it later on. By adding all this modifications u will decrease the car's re-sell value while U have pumped a lot of money into it. Unless U are absolutely sure U are going to keep the car untill it dies I wouldn't do it.
If I had the money i'd buy a porsche to race and a sl for everyday use...
It all depends how for U wanna go, it's do-able but not an easy job.
I'd like to be proven wrong though ;-)
Good luck! | 
