Quick roundup of the 3 Mazda 6 sedan's (since its confusing)
Mazdaspeed MPS 6 (274/280)
3,630 lbs
Mazda 6s MTX (220/192)
3,243 lbs
Mazda 6i MTX (160/155)
3,042 lbs
Here's some competition...
Evo MR: 3,263 lbs
STi: 3,260 lbs
Legacy GT: 3,300 lbs
SRT-4: 2,900 lbs
Rx8: 3,029 lbs
G35 Coupe: 3,512
350Z Eth: 3,197
Mustang GT: 3,450 lbs
The specs and reviews of the MPS 6 put it at 0-60 of about 6.4-6.6 seconds. Just about the stock time from the 6s MTX. 1/4 mile estimates put it at mid 14's. (Stock 6s MTX's run high 14's). The MPS 6 rev's low, with all its grunt down at the bottom end of the power band, completely opposite of the other 6 models. Think VW's torque band, and thats about an MPS 6. Lots of pep off the line, quickly trailing off.
Obviously you can see why the Scca Pro World Challenge has annouced they will NOT be using the MPS as their racing platform, and will be sticking with the lightweight 6i mtx. (est 2700 race weight)