ive started with a problem with my vauxhall astra 1.6 16v mark 3 i was traveling home and it started to hesertate and after a while when setting off from a junction it seemed to have no power at all and felt at time to be running on 3 cylinders and was drinking alot of fual when i finaly nursed the car home it didnt have enough power to get it up a hill near home ive checked the ht leads spark plugs and air filter there,s no water in the oil or oil in the water to indicate the head gasket has gone the car will fire up but when warm it struggles to rev up so setting off is a problem but when you can get going at first it sounds its on 3 then runs fine and maybe once every 10 minutes the yellow engine warning light comes on then goes off .
like i said ive checked the plugs ht leads and filters and head gasket could there be any other thing to look for ive also looked for and loose wires or viserble breaks in wires .

does any one know the problem