The Luftwaffe aircrew had little idea of the capabilities of our 'Radar' system in the early days of the war and so certainly some solo bombers did alter throttle settings in an attempt to confuse detectors...
From Peter Stahl 'The diving Eagle'...
Target Liverpool march 1941 ...Heavily engaged by searchlights...
''I try every trick I know to mislead them,but in vain,every time i change direction they follow me.Even the usually effective method of deceiving the defenses,by changing the revs of the engines to alter their sound,fails this time''.
Who knows...inland it may have been effective because I doubt there was much inland radar coverage early in the war.