In my own personal experience, oiled filters don't make any kind of difference performance-wise and cause more problems than they're worth. Depending on your intake setup and location of sensors (MAF, IAT, TPS, etc.), the k&n may cause problems even if oiled properly. That's what happened on the Chevy; cleaning the intake tract and throttle-body thoroughly and dropping in a FRAM tough-guard filter (which is a damn good filter btw) solved the problem immediately.
IMO, my vehicles perform better with paper/oil free air filters. Also, as noted earlier in this thread, OEM-style filters do a better job of getting all the dust and pollutants out of the incoming air compared to k&n's.