Loud Intake Sound

The past couple of months my car for some reason my intake makes a very
loud humming sound I would describe it as if I'm going a constant speed
such as 40,45, 55 and such.  I know it makers a low humming sound when I
accelerate but this is a very loud sound.  When I start my car from a cold
start RPMs will shoot to around 2,500 go back down to around 1k then right
back up to 2.5k and then drop and somtimes the engine will surge and that
loud humming will go in and out with the surging of the engine.  I've talked to
different mechanically inclined friends and they have no idea what's going
on.  I do have a K&N cold air intake installed on the vehicle with a fresh filter
on it the old one was damaged rubbing against the bottom splash guard.  I
recently replaced the fuel filter, spark plugs, changed the oil, changed the
suspension, also replaced the IAC, TPS, MAF, and cleaned the throttle body
and the EGR valve.  I know when I slow down coming to a stop the engine
will feel like it's about to turn off and the lights dim which would mean the
alternator.  Would that have any effect on the cold air intake being so loud
when I'm just driving down the road?  I'll supply any other information I need
to as I don't know what else to do besides to try and find a mechanic that can
actually help me.