Thanks for your response. Ignition/fuel system divided into lane A lane B power loss first noticed on climb out from same runway under similar weather conditions and take off weight. Previously circuit altitude reached on crosswind with reduction in power required downwind to prevent over revving. First indications were in circuit where aircraft took to 25% downwind leg to reach circuit altitude and no throttle reduction required to prevent over revving of engine and continuing slight decline in performance up until now. engine diagnostics dongle information forwarded to Bert Flood with nothing to indicate any faults. fuel pumps replaced on advice from Floods with problem persisting. filters/plugs checked, leakdown test performed. Ignition modules exchanged, prop balance checked.