I chose to not pull air from the air cleaner for my onboard air. Here's why: the pressure in the air cleaner is lower than atmosphere, not much lower but it is lower because the engine is pulling air through it. Any drop in the pressure at the intake of the compressor will reduce its efficiency. Think of it as the opposite of a turbo charger. One of the nice benefits of an engine driven compressor is the relatively high air flow. Why reduce the flow by drawing air from a low pressure zone?
'03 KTM 450EXC
"If you know what you're doing, then you aren't learning anything." - A. Lincoln