At the end of the day the only way to get the 335i close without dumping a ton of money on an upgraded turbo will be with downpipes, which add about 20lb-ft, and a somewhat aggressive tune. Makes a big difference in low-mid range power + faster spool up. Would also recommend getting an intercooler to keep that power consistent during multiple fast runs/hot weather. With those three things you could easily get a car that makes 400hp/420lb-ft of torque or so in a car that weighs 350lbs.... and if you have the 8 speed transmission, closer gear ratios to help a shade with acceleration vs. the CTS-V tranny.
This car will never without hardcore mods get near a CTS-V's feeling of uber torque, but you can cut the gap in half IMO. But if you want to talk about modding cars, modding a CTS-V would have been a better option.
Last edited by verbs; 08-10-2012 at 12:56 PM.