Best Mods.....
Get a tune:
http://www.xbimmers.com/forums/showthread.php?t=1030167
Exhaust is a must, there are a few options depending on if you are keeping the car or not. The stock exhaust makes the car sound like a sewing machine, there no soul there.
Spacers, 15mm front & 20-25mm rear.
The sky is the limit, well maybe your wallet is. Post some pictures.