I'm hoping get some suggestions on what could be causing a problem I'm experiencing with my 2003 Osprey with 245dl.

When running wide open I typically get 3900rpm, but lately it drops 600-900rpm for no apparent reason. Periodically, but then at comes back up. The lag will last anywhere from a minute or two and the climb back up or it can last 30 minutes.

I've recently changed the fuel filters and air filter after the problem started.

Any suggestions are really appreciated.