1/2-3/4 Throttle Bog (help needed)

Ive heard folks say that bogging between 1/2 and 3/4 throttle can mean Rich or Lean. Help me understand what I have going on.

Bike Summary:
02 WR426
Stock pipe with Pro Moto baffle
YZ Timed & 03' 450 Cam
Stock Jetting
AP squirt: 1sec
Float: 8mm
Temps: 65-80F
Elevation: 800'
Air box lid removed
Air Screw: 2 turns

Performance Summary:
Starts and idles good. Good/smooth throttle response when cracking open from a stop.
Once I get past 1/2 throttle engine bogs down until I throttle back.

So far Ive tried a 170main and the stock 165 main. Needle clip is on #4 (middle). Im off to try the #5 clip position in an attempt to lean it but wanted to confer with the experienced on this before banging my head further.

Actually, I just got the bike off another fella. Upon receipt of the bike I tore down the carb, cleaned, checked float, and made note of the current jetting for a baseline to its current performance. So to answer your question, its had the bog since I got it.
The bike is taken to op. temp everytime before taking note of performance. At first I thought it was an over oiled filter but its not.

At this point my plan is to adjust the AP squirt just a bit, note response. Then change to a YZ needle which is more rich across the circuit.

I still think this bog is a result of a lean condition which is why I want a richer needle to play with. But, since my experience is limited I'm looking for confirmation from the experienced. Thanks guys!