so my car has seemingly developed a new vibration that only shows up between around 43-50 mph. i don't think it's RPM related because it shows up regardless of what gear i'm in, although the RPM does seem to affect the way i feel it. in 2nd gear i barely feel it because it just feels like the engine working, in 3rd i can def feel it but the vibration feels...tighter, if that makes any sense. and in 4th and 5th it just feels like a looser vibration.
it's kind of like the difference in feeling the engine work at 4k RPM in 6th at 73 mph vs 900 RPM in 6th at 20 mph.
the car is mostly stock with K&N FIPK, FUJI catback, lowered on Tein S-techs.
it's not a CV inner cup issue, as i did the side to side swap about 6 weeks ago and there was no wear on any of the cup walls whatsoever.
it's hard to diagnose where the vibration is coming from because i can feel it both in the wheel and in my seat.

any thoughts?

thanks

 

Wheels out of balance? Out of balance tire usually propagates around 45mph and again at 90...

 

not likely...it happens with both my AP1 and AP2 wheels on

 

anybody?

 

bueller?

 

I thought about balance too. But maybe lug nut arent tight?