There isn't one on the 2.2l ecotec
22L (liters) is 5.81 US gallons.
Ther is no egr valve on the 2.2 turbo engines. With FI and turbo, there was no need. Some of the earlier carb engines did have egr.
I changed the EGR valve, PVC valve, now it has gotten worse. I also cleaned the throttle body.
lr stands for long rifle(uses a bullet) I dont know where you got 22l from
Generally when the head gets replaced you would also want to replace your plugs as well. It can sometimes be a result from where the water has traveled into the oil from a bad head. I replaced mine with bosch platinum 2 and haven't regretted it for 2 years.
Impossible to answer without more information
50-200 usd
10-1000 USD depending on specifics.
20-50 or so
No published sn data.
100 or so
Can vary from 100-400 USD or so