Didn't want to post this in the main M3 forum because I do not want this to devolve into a 335i vs. M3 debate. But Dinan just announced their Reflash tune for the 335i and it's a pretty healthy 384hp at the crank. Price is also pretty healthy at $1,999, but Dinan covers the manufacturer's warranty. While I know an extra 84hp doesn't transform a 335i into an M3, it is a pretty enticing option, especially since you don't throw your warranty out the window. More here:
http://www.e90post.com/forums/showthread.php?t=99843