[MikeR1994]

If you're ok with not keeping it NA, a supercharger from MMW (not quite on the market yet as far as I know) or ARMA would be the way to go:

ARMA kit (no clue about cost): http://www.armaspeed.com/eng/goods.php?act=cat&no=22

MMW kit ($6,500): http://mmotorwerks.net/component/jsh...ct/view/12/145

If you want to try and make more NA power than anyone else (dedicated race cars excluded) I've heard of:

Active Autowerke stage 2 tune($499): http://store.activeautowerke.com/act...ware-p149.aspx

MMW ceramic coated race headers($1,100): http://store.activeautowerke.com/act...ware-p149.aspx

Noelle Motors stroker kit (Around $16,000): http://www.noellemotors.de/3_2l_engi...7f2dc4c.0.html

Things that will work for both:

Lightweight wheels. Apex ARC-8's look good for how little they weigh:
http://www.apexraceparts.com/3-Serie...E902_c_19.html

JB Racing Lightweight aluminum flywheel to get more power to the wheels ($629.95): http://store.vacmotorsports.com/jbr-...dsg-p2433.aspx

Aaaand we're done here