340 with som problems

ok the powerloss and fireing in the exhaust seems to come from something wiht the iginition on closer inspection using my timing light it seems to forget to give a spark from time to time but it seems to turn over 3-4 revolutins with proper spark and then it does not spark for one turn and then it sparks 3-4turns again very strange must bee some loose conection somewhere just havent found where its a complete MSD ignition system and basicly everything exept for the distributor "base" is new for this season so it does not have so many hours of run time on it, havent had the time to check the compresion yet but i have found three pushrods that used to bee straight that now is slightly bent those are now replaced with some other spare ones with the correct lengt not worried about holes in the rockers since they are crane goldrace roller rockers forgot to give some spec on this engine that is a pretty wild streetengine with only 4"hg of vacum in gear with a lose converter, somthing that came to my mind on that single white sparkplugg is that it may bee a vacumleak somewhere around that cylinders intake port, have too check more things tomorow
i used to have 135psi compresion preasure measured turning the engine over with the starter...
thanks for the help i will also try to listen to where it knocks from!