If it's the same as mine (1997 1.6i 16v ECOTEC) then Haynes manual says you need to get UNDER the car - to extract ICV from under the inlet manifold ! I had a mis-firing problem when engine was warmed up ( see post 24/02/2006 ), turned out to be the ignition leads. Forget about buying leads from VX dealer (£143+VAT !!), use Autovaux or other cheaper suppliers
Sam