well from the start i had a bit of a oil leak cos the rocker cover seal wasnt in properly so i took it off cleaned it up put it back in, hooked everything up, turned the keys and it was idling like a prick, kinda shuddering seemed like it was running on 5 cylinders or something, so i gave her a few revs see if it would clear the throat but no go. so i fiddled with the spark plugs, cleaned the throttlebody and the isc, but still no go.im fairly sure its the leads because i got dad to pull the leads off one by one and were pretty sure no.2 wasnt sparking. but yeah any other theories?
cheers

possibly ya map sensor or a real bad vac leak.
check if theres spak coming through all leads.
maybe the dizzy could be stuffd

vac leak. if your not sure about #2, get a multimeter and check for resistance

When you replaced the rocker cover gasket, did you replace the rubber grommets under the bolts????
Did you over tighten the bolts????....They have crush tubes, so you can't force the rocker down any further. The grommets are what holds down the rocker cover.