started my glanza up this morning and it took ages to get going and noticed straight away it was misfiring. so changed the distributor cap, ht leads, and spark plugs... but still no spark on cylinder one.... but when i rev it up above 3k it starts to make a tapping sound like metal on metal......? no smoke and just had the headgasket done about 2 weeks ago. engine mods: zisco mani, zisco decat, tail wastegate, fmic, relocated air filter and running 0.6bar of boost. any suggestions?