When doing your service, one thing to be cautious of with the Z22SE's is changing the spark plugs.
Be careful when undoing them, especially on cylinder 4 (gearbox end) as if they have been tightened too much it can crack the cylinder head and render it useless as a coolant gallery runs very close to it.
When tightening the new ones, ONLY torque them up to 20 N-m / 15 lb-ft
The GM Part # is 9199038 - Triple Electrode Spark Plug (equivalent to Bosch HLR8STEX)