It is not the timing.....
Sure, reducing timing will 'fix' the problem but you will be making the engine less efficient.
50* at cruise is not excessive for a long duration cam. Long duration cams require more timing at idle, cruise & lower speeds because the increased overlap dilutes the A/F mixture which causes two problems: leanness & more time for the mixture to burn as completely as it can.
Richening the cruise mixture slightly will fix the problem & require less throttle opening [ more efficient ] for cruising.