my Corsa SRi 8v someimes accelerates erratically. Happens more when the engine is warm i.e. after sitting in a jam - especially when going up-hill. When driving at a constant speed (30/40ish) it jerks unless i drop a gear/ put my foot down. I have done the obvious things like removing my induction kit, replacing h/t leads and plugs but it continues. I know a diagnosis is tricky but has anyone got any possible suggestions as to the cause of the problem