Bit confused about the Specs + Car comparisons

firstly i have read in another thred in this forum that the target weight of the SLR would be 1400kg. It has a body made out of carbon fibre, extremely powerful engine and accelerates very well. However web sites say that it actualy weighs around 17xx kg which is a hell of a lot more than wanted. It is adleast 500kg heavier than the zonda yet is a hole 3 seconds faster round the top gear race track. Although it does have more power, the 500 extra kg would make it handle like a dieing cow but yet it habdles like a dream and brakes from 120mph to 0 in less than 60ft. It also takes just 28 seconds to get up to 300kph and 0-60 is around 3.6 sconds. All these facts say that it must weigh around 1400kg yet 2 reliable web sites say it aint so and gives it a curb weight of 1700kg..Can someone please explain?

The number put up by Mercedes-Benz USA is 3748 lbs, which translates to around 1,700 kg (dry weight)

i now but the specs of 0-60, lap times etc all cry out something a lot lighter. plus if the whole car is made out of the carbon fibre composites then it cant weight as much as my dads saloon!! whats stupid is mercdes benz uk (which is more accurate towards cars, as they are less biased) says it weighs 1400kg

A car less than 3800 lbs is considered "light" for a Mercedes vehicle (SL 600 weighs about 400-500 lbs more).
Also another problem is whether the magazine editors tested a pre-production version (whch may be lighter due to the lack of stereo, a/c, etc..maybe even a "secret" power boost)or a REAL production versions that are being delievered to the customers.
Recently Mercedes has been conservative about its power rating, such as the 55 kompressor AMG and the 600 twin turbo engines. Although Mercedes claims the same horsepower rating for both, but many dyno tests had found out where the 600 twin turbo is a lot more powerful.
Car and Driver tested a SL600 which ran 0-60 in less than 4 seconds and clearned the quarter mile in 11.9 second @ 120mph.