Several of the freon solvents are effective and safe but unfortunately they're hard to come by these days. For cleaning, remove the electronics and wipe the Karman pillar with a dry cloth. Make sure the pressure sensing holes are clear but other than that leave it alone. While its out clean the plumbing with anything you want.
Filters: What Typhoon said. A paper filter will flow all the air the engine needs. Filters are rarely the limiting factor in an induction system, something that can be easily checked with a manometer. Remember, flow only matters at WOT. Otherwise there's always a restriction in the system...it's called the throttle plate.