I've opened up both the top and bottom of my air box (and the bottom of my K&N filter), and wonder if I should still consider the polaris bell mouth, or if it would even fit with the top of the air box opened up.

Smaug - when you check your spark plugs keep in mind that you're only checking the reading of the engine at one speed. If you kill the engine when it is idling that's the reading you're going to get from the plugs. If you want to see how the bike is doing at cruising speed, you need to be at cruising speed when you kill the engine to read the plugs. I suggest you find a straight stretch of road where you can kill the engine and coast to the side of the road, then check your plugs. That will give you the cruising speed reading of how the engine is doing.

08 America, A/I &, Calif emissions "stuff" gone, air box removed & battery relocated, billet intakes, UNI Pods, 145 mains, 42 pilots, Stage 2 igniter, intminators, 813 cams, Progressive 412's, modified seat.