Wowww Dinan 4.6l! I'm soo jealous, but as you were saying I was expected much higher numbers than that. You should get at least around 450whp with the engine, exhaust, intake. With the x-pipe you should probably get another +20whp?
A stock M3 gets around 340-360 on the dyno. But then again it depends on the dyno that you used as well as the temperature and what not.
What dyno were you using? Because something doesn't seem right.
M3.E90 JZB Blacked out.Coded.TurnerTestPipes.GTSDCT. Magnaflow Rear. Dinan Tips.