Thanks for showing us your testing Mr.5 Your findings are not surprising at all. You should of added more boost and seen the differences which should theoretically grow between the two.
You will also see a completely different picture between the IAT's.
As a side note fan speed is measured at the cowling of the fan. Drive the car at 60mph and try open the door or stick your hand out the window. Its very hard for a dyno to duplicate that. On the road the Stock Airbox will benefit less from under hood temperatures than the dual so the difference in gains might be marginally better than your test.
All in all I am very close to installing my stock box again. Most importantly for peace of mind of its filtering capabilities, its reliability and the fact that I most often running less than 14.5psi.
08 E90 335i AT RB Turbos -NX Wet Kit - Chiplogic Flash or Procede V5- M3 Diff - AE Exhaust- Forge Dv's - Helix Intercooler - AR DP's - P3 Boost Gauge - Vishnu Meth- Stett Chargepipe and CAI