So you have bolted on a big turbo and tuned your Subaru to the max but still aren't hitting the peak numbers you are after. Untangle your skirt and dry those tears. The Invidia large diameter header for the 02-07 WRX  STI maintains the all of the great features and design incorporated into all Invidia products, but takes performance one step further by widening each exhaust runner for a product specifically designed for but turbo applications only. Wider diameter runners provide exhaust flow unmatched by any other performance header or port job, supplying your turbo with the smoothest, turbulence free exhaust stream possible. This translates into faster spool, better response and most importantly, more power! If you are looking maximize peak power on your big turbo setup and don't know where else to turn, this is the answer. Because this is an equal length header, this product will only fit 2.0 WRX models when they swap to the 2.5L STI/WRX oil pan

This product is not recommended for stock cars or smaller turbo upgrades.