Distributor gear wear can show those symptoms. Improperly set distributor can too. With my truck it was at speeds over 40 with very slight pressure on the gas pedal, sometimes a misfire would register and sometimes not. You need a scantool that will show the parameter cam retard or camshaft offset- the difference between the CKP and CMP signals. Yours is probably negative by 8 degrees or more(probably not -15 degrees or you would have a p1345 code)