Power Loss on Takeoff

Yesterday I experienced a slight power loss on takeoff.  Run up was fine.  Full power takeoff was fine.  Once I hit pattern altitiude, I pulled the power to cruise climb and there was a noticable decrease in power/rpms.  It only seemed to happen in the mid-range throttle position.  When in cruise, I slowly advanced the throttle and when it hit the mid-range position, the rpms would drop slightly and as I continued to advance the throttle, it would suddenly increase rpms by 500-600.  Fuel consumption seemed to be higher than usual as well in cruise.  Any idea on what may be going on?  I plan to do a BUDS download on Monday, but I'm curious if anyone else has had this issue.  PS - Never got a lane light.