vauxhall astra 1.4 ecotec miss fire?

hi i have a 1997 vauxhall astra,when first starting runs fine then after about 2 mins will start to miss fire.
i have replaced plugs,leads,coil pack,lambda probe,air temp sensor in inlet pipe,secondary air inlet valve unit,checked valve timing,carried out a compression test (all ok).cleaned throttle body,even disconected battery to let ecu power down.but none of this has made any difference. also when it is running i have removed plug leads in turn and seems to be no.1 cylinder that makes least difference with lead off.also miss fire seems to go when at higher revs.if anyone has experience of this type of problem please let me know.thanks.

mark 42
April 2010