Firstly thanks to Duncan for letting me put this link up as its not part of the club and not a club Approved trader.
There seams to be a larger interest in tuning the petrol 2.2 at the moment, whether it be the Z22SE or the slightly different Z22YH (direct).
The 2.2 has 2 main restriction in power available, that being the inlet manifold and the zorst manifold. The stock items being very restrictive.
2.2 owners may be aware of a mod that Vid has completed, fitting a Ecotec 2.4 inlet manifold as a direct replacement to the stock 2.2 manifold.
The one on the left is the 2.4 and the one on the right is the stock 2.2 manifold. As you can see the runners are far larger than the stock 2.2 so allowing better airflow giving better bhp and torque in the mid to higher rev band without loosing any at the lower end.
This manifold unfortunately is only available from the U.S. as such getting hold of one delivered isn't cheep, your talking £200+.
Courtney Sport however have agreed to do another group buy in conjunction with the 2.2 forum z22se.co.uk. The price of the group buy Manifold delivered to your door is £125 which is a great saving over the stand alone price. If anyone is interested the group buy the thread is HERE
Although this mod has now been done on many vx220's, Astras and Vectra b's, so far only Vid has fitted it to a Vectra C, well done mate, Vids thread HERE
Fitting the manifold also requires some other things like a new bracket for the ECU and dipstick, both which can be made yourself but are available to buy on the 2.2 forum. You will also need to blank the EGR off, the plate is available from VX for about £5, a suppressor as the alternator needs a small mod, some servo hose and some longer bolts for the ecu.
Some other links to info on the manifold HERE and HERE
Any questions I will try and help, but your better posting on the 2.2 forum. tks to Vid for the extras info.