Here's a calculator.
http://www.secondstrike.com/Technica...leanerCalc.asp
Mine is the following with RedBarchetta's filter he described above
622 PHP @ 5800 RPM 482 CI, high performance street
oval, oiled felt, 8.5 x 15 x 2, 1 filter
RPM Pressure Loss (percent) Horsepower Loss
3,800 0.40 % 1.77
4,300 0.54 % 2.89
4,800 0.68 % 4.10
5,300 0.80 % 5.08
5,800 0.88 % 5.47
6,300 0.91 % 4.99