This evening , i decided to try some more aerobatics , preflight checks in the hanger , showed all green in the engine , reasonable compression check.
Fuel in wing tanks only , i started the engine , and let her warm up ,ASN giving real weather , once engine was warmed up , i gently increased revs for mag check , right mag failed check , shut down , and went to hanger , looked in the engine , both mags showed green , mag switch marked left/right , but engine its mags 1 and 2 , not knowing which releated to the right mag i clicked on both mags 1 an 2 , restarted engine , and she then passed mag check and supercharger check , taxiied to runway 31L at KBFI , as the wind had gone from calm to 3knots crosswind for rwy 31L , started takeoff run , just as i was lifting off engine well within the max marks , there was a bang , and an oily puff of blue smoke came from left exhaust bank, quick glance of inst showed nothing unusual , oil press/temp good as was fuel press,engine sounded ok and a quick check of throttle response showed the engine was willing , all this while retracting gear and trimming for flight , did a circuit and landed , on shutdown , and going into hanger , there was a message saying check engine , everything showed ok , till i did compression test , a cyclinder had blown , now repaired.
regards alan.
Thank you for sharing. I on my hand had a different sort of unexpected experience with my P-51 (civ). Sim platform and computer in nature, I had to reinstall it due to some recent CTDs (without errors in the event viewer). 
It's back online now, but I have a brand new P-51. I have the old data files, but I'm afraid, if I place them in, it could CTD again (I may experiment).