4250 RPM ... what's going on there?
 

Ok... my car is stock... just a cone filter in the stock airbox.

Obviously with the cone-filter I can hear a little more engine than with the stock panel-filter, well, it seems as though when I'm WOT and as the revs pass 4250 the engine seems to get louder.
I'm not talking progressively louder, I mean, like a light switch. Once it passes 4250 it's like my ears just popped and it's a little louder. I don't mean super loud or anything... the only thing I can think of comparing the noise difference is like when a Civic hits VTEC.

Is there something happening at that point in time, or are my ears playing tricks on me?

Yes the ports open up.

Read the stickies in the tech section.

As far as the intake goes, between 3250 and 5500 RPM the secondary shutter valve opens to allow airflow through the secondary intake passages.
The engine is using two intake pipes and two intake ports per rotor.

did you remove the VFAD when puitting in the cone filter - that may explain it ...

oh god i am selling my 8 now

No need. I'll crash mine into yours so we are both taken care of.

No, I left the VFAD in tact