i sold my 2002 astra sri turbo which is the same as the gsi but a limited run,
i loved it and only sold it as its not that suitable for a new baby,
as for power i spent alot of money on mine, big intercooler, vxr turbo, cdti airbox, remap.....................etc
not to disapoint but you cant get 350bhp form a z20let without changin the internals and for the price you would be better putting in a z20leh,
max is just over 300bhp and thats pushin it