hi there, i have a vectra b x16xel that i just put new head gasket, 16 new valves and new stem seals due to slipped cam belt, i started it and it runs fine for 10-15 mins but as it warms up starts to smoke slightly, then if i leave it ticking over it starts to missfire, at this point if i drive it down the roads it puts out a road full of smoke and smells like oil burning kinda smoke that lingers for ages, this slowly clears after 5-10 mins of hard driving or if i rev it hard and stay still then the same shed loads of smoke and after 5-10 mins revving clears up and missffire goes until ticking over 10 mins or so and comes back. i read somewhere that when installing stem seals you cant push them on too far or they open up or not enough n they get hit, well i hammered each one on quite hard, how am i supposed to know how hard or far to put them on and do you think this could be my problem, also how can i prove this, what if i run it till it misfires n remove plugs or something could i tell??

what is wet / dry compression testing, dry i assume is normal compression test what is wet?? and would this prove it was stem seals or rings?? or other?

many thanks