Buy the JB4 Stage2 with the downpipes and you will be all set. Its pretty pointless getting downpipes without a tune IMO.
BEST PRICES GUARANTEED
JB4 **G5** On Sale - FREE Shipping Click Me - NEW JB4(N55) & DCI's $95.00
NEW F30 N20/N55 ER Downpipes and Chargepipes - BMS OCC (On Sale)