Are you aware that K&N filters trap very little of the grit going into your engine? There are some good articles on the web about racers who have run K&N filters and performed engine leak down rates (indicating piston ring wear) before and after races using K&N versus paper air filters. The K&Ns are just marginally better than running no air filters.

Overly lean mixture or hot combustion temperatures may be caused by not enough fuel pressure, clogged passages in the throttle body (if you have one - maybe yours is mechanical?), clogged fuel filter, weak pump, timing out of adjustment, incorrect spark plugs (too hot), bad thermostat or water pump causing high coolant temps, etc. Make sure to fix the simplest (cheapest) things first,