Two common areas for idle faults are the throttle body needing removing and cleaning. Or a vacuum leak on the inlet side of the engine somewhere. Using brake cleaner sprayed around joints and pipes, if the idle goes up there is a leak there.
Does the car drive ok once off idle?
Hard to say where the leak is from those photo's. It doesn't look like it has the normal pink coolant stains visible. The pipe has an O ring at each end, you need to remove the housing for the thermostat/coolant temp sensor to get the pipe out so get a new seal for this as well.. There is also a...
Stage 1 cams are very mild with only a minimal gain over a standard cam and will work ok with the standard valve gear.
I ran the DBilas cams for quite a few years and around 70k miles with no other internal engine work. They are a nit more aggressive than the Comp cam stage 1.
Swapped to the...
Your best off speaking to evocarlos he is a bit further away but does offer a very good service using top quality parts. He does these chains in his sleep now and I believe offers a "while you wait" service, You will not find anyone better than he is at them now.
Just regular oil changes at every 5,000 miles or yearly which ever comes first. Only use 10w40 semi synthetic oils as well. Only done 20,000 ish miles in the last 11 years while it's been in Corsa's :LOL:
My Vectra B died over 11 years ago, 150+k miles on it but she was rotten underneath the cover sills where they all go.
Don't see many Vectra B's on the road now. Still a lot of older Vauxhalls about though like Cavilers Corsa B's and Nova's.
You can use the Saab B207 oil cooler but I think you have to modify the thermostat housing in some way to make it fit with the rest of the Astra G parts?
You can use either sump pan.
The rocker cover is best to use the Z22SE one but you have to plug and blank the exhaust cam where the brake...
When I got my first Z22 the main dealer and all the tuners recommended that it was only run on 99octane fuel. Now with E10 out there as well it is a must to run them on E5/99 octane fuel for best results in MPG's and engine life. Even more so important with the direct injection Z22YH as already...
For a simple build the Courtenay mapping is good. I have been using it in mine since I went supercharged with no faults. Total price base map and rolling road tune was around £350.
Plenty of guides on here on "how to" EvoCarlos fitting guide is the most recent and lists all you need.