same old story mate, you pay for what you get sometimes.
just had an e-mail back from the vauxhall guy in the UK and the original equipment ones / part numbers, sodium filled exhaust valves
Inlet valves, 90322694, I can get these in Mahle who are OEM parts
Exhaust Valves, 90322697, i can get these in Mahle who are OEM parts
yes there is conflicting stuff on the net about sodium exhaust valves being used on early C20XE only. I will go with what my guy at vauxhall says, and that's sodium filled.
interesting read on why sodium filled valves are used here
http://www.aa1car.com/library/ar1192.htm