IAG Performance Street Cylinder Head PackageIAG 600 STREET CYLINDER HEADS PACKAGE FOR 2015 2021 SUBARU WRX POWER RATING The IAG 600 Cylinder Head Package has a power output rating of 600 BHP ENTRY LEVEL STOCK REPLACEMENT HEADS The IAG 600 Cylinder Heads are designed to function as an entry level replacement for stock OEM 2015 2021 Subaru WRX heads. If your engine has suffered a catastrophic failure which requires replacement of your cylinder heads, or if you don't have OEM heads to start with,