I was really impressed with how well this combination came together utilizing the US EJ20 heads and a set of good cams. I’m a pretty conservative tuner when using the dyno as I understand how much can change in the real world. At peak power the AFR was 11.1, boost was 19 psi, and ignition timing was only 18 degrees but the results were pretty spectacular. Spool up was also great as 18 psi was realized by 3600 rpm.
EJ257 short block
CP pistons by AXIS with cometic gaskets
EJ205 WRX Heads
Stock WRX springs
STI shimless buckets.
Kelford 264 intake and 272 exhaust Cams
Ported WRX exhaust manifold
Uppipe with 38mm tial gate,
3″ midpipe and prodrive oval tip exhaust.
All components, including heatshields, jet hot coated
FP Green turbo
blitz boost controller
800cc (modded stock injectors)
knife edged throttle body
Element Hydra EMS
Hyperflow front mount and intake
Samco MAF hose and inlet
Given these results I think many should consider going this route instead of the AVCS JDM heads or the US STI heads.
I would definitely say if AVCS was not going to be utilized the better choice is putting cams in the WRX heads but it’s so easy to run AVCS with the Hydra EMS. At this power level I can’t tell you definitively what heads flow better but I’m leaning towards the WRX heads with cams. This is mainly based on the boost level, ignition timing, and AFR run on this car to achieve this power level as it compares to an STI with the same turbocharger. On an STI I usually see about 350 whp at 19 psi vs. 380 whp on this car.