Stop Blaming the filters.  The oil pressure switch that operates the oil
warning buzzer above 2000 rpm is located between the pump and the filter
inlet.  If a filter was more restrictive than stock, than this switch would
see a higher pressure and would be even less likely to cause a warning.  If
the filter was less restrictive, which caused the light and buzzer to
activate, than the engine bearings would actually be getting more oil.
Below is a list of the reasons I've found for the warnings.

1) Incorrect or defective pressure switch.
2) Poor wire connections.
3) Overheating engine.
4) Incorrect oil viscosity,or oil diluted.(20w-50 as per owners manual).
5) Crankcase overfilled.  Changing filter usually corrects this due to 1/2
quart lost.
6) Pump inlet screen partially blocked with crud.  Causes problems after
warm up.
7) Engine just plain tired.

Dennis