Check your old purge valve to verify it isn’t clogged. Sometimes when a canister fails, it’ll shoot carbon pellets through the lines, which can end up at the valve and clog it. Pellets keep clogging the purge valve until you clear the lines of those pellets. When you disconnect the line, shake it. If you hear rattling, then there are pellets in the line. You can also inspect the inside of the purge valve for carbon pellets. I had to disconnect all lines at their connections and blow them out to clear the pellets when this occurred on my truck.
As for cylinder 4 issue, you can also rent a coolant pressure test kit from like Autozone to see if your coolant system can hold pressure. If you have leak down, then it confirms a leak. Pull the spark plug from cylinder 4 to see if it’s wet or cleaned off compared to your other plugs.
Note that if you have a coolant leak in a cylinder during the test, you’ll want to pull the plugs before cranking it over, or else you get hydro-locked (best case) or bend a valve or connecting rod if the leak is significant enough.
