does it change on all the other cylinders when removing there leads. it could well be a fuel injector get it pluged in it might say what injector or weather its an injector driver fault in the ecu. ive not seen a st for along time see if you can swop injectors around to move the miss fire to another cylinder.no1 is down you say no1 this one should be the timming end if its no1. your not getting 1 and 4 mixed up.its worth putting a brand new plug on that cylinder thats miss fireing plugs arnt as good these days when they get fukered they dont like the cold start fuel. no4 valve looks good by the comp test youve described. have you any symptoms of head gasket problems