If you want a super fast AWD car, you should look into the Audi S4, RS4, 335 xDrive, Subaru STi, Mitsubishi Evo, etc...
The E46 XI is not and should not be your starting point. That said, there are plenty of supercharged XI's on here but I'm not sure any have nitrous. The cost of adding such a system to an XI would negate any cost benefits from just going with the proper car in the first place mainly due to the substantial maintenance costs of getting a used 10 year old car to the state it needs to be before adding 150+ awhp.
Last edited by SamDoe1; 12-28-2012 at 10:18 AM.