My .02cents.....Take it to a track and run them. That way you have a timeslip to back it up.
My experiences with WRX's is that they are a bit doggy. I raced a new WRX from a stoplight one time (I know, I speak out against street racing all the time. It was 2am with no other cars, pedestrians or anything else.) and held with him (even though he got the launch). I don't have much done to my car and wouldn't expect more than a little over 220 to the wheels. Plus my clutch slips at higher boost. We also did a roll and I began to walk him after second gear with a little over 3/4 throttle. I don't know much about their gearing, but it doesn't seem like it can hang with a DSM gearing. Plus, their trannies are even more frail than ours.
You guys have comparable hp. I think you should be able to take him as long as you have it tuned right for your fuel. It will probably come down more to the driver and how well you know your car. I mean hell, I beat a modded twin turbo 300ZX at the track because I had a better launch and 60' time. If we went from a roll, he would've slaughtered me. And that was before any mods on my car.
Plus that valve cover adds about 75hp to the wheels
