1) The SPF calculator is well worth the time and effort.
2) Use the largest dia and tallest K&N (or Accel)
oil based cleaner
3) Check the difference of the car with the AC on and off in regards to a dyno pull (or 1/4 mile runs, at least 2 each).
The most important factor is to get rid of the plain paper element. A K&N element outflow the plain paper element by a huge factor.