Cylinder #2 Misfire-after intake manifold replaced

Bad spark plug ignition coil's do that too. Cheaper. $50. #2 cylinder is the middle one on the rear bank which is closest to the firewall. You'll need to take off the top intake to get to it.

Check the intake manifold gasket. If it leaks it will draw air into engine and this air bypasses the mass air flow sensor which will cause a rough idle or running symptom from running too lean. If you change the intake manifold gasket you should probably change the valley pan gasket at the same time. A dealer will change both for less than $500 and you might save some more if you dig around on GM Service website and find a coupon discount (Usually 10%-20%). You might save more at a local shop if you trust them and they do this type of work. Getting to the intake manifold gasket also exposes the valley pan and since you are already there it only takes a little more to change that gasket too. Some GM V-8 engines use a little oil between oil changes and if both gaskets are meticulously changed at the same time it will sometimes fix the oil usage. It did for me on my Tahoe (126k miles).

swap the injector with another cylinder and see if the misfire follows the injector or start with a compression test

What engine do you have in your Nissan that has the misfire, how many cylinders and how many liters???

Intake manifold gasket ,try torqueing intake bolts,or spray carb cleaner around bolts and seem while running see if it rums smoothly while spraying if so new intake manifold gaskets needed. YouTube video check to see.

Very common the intake manifold gaskets leaking. I've replace tons of them. They can **** air internally and cause a misfire.

Sound like an air / vacuum leak to me.
Re-check for an air leak on #2 cylinder inlet manifold.
Use a propane torch (unlit, of course) to flood propane gas around inlet manifold/head flange & gasket area.
If there is any change in idle speed during this test you have a vacuum leak.

It could be burning and you don't notice. Remove air filter box assembly from top of intake manifold. Hold throttle wide open (engine off) and look through throttle body (flashlight may be required) and see if oil is puddled up inside manifold. If so then the intake manifold will need to be removed so the lower pan gasket can be replaced.

spray carb cleaner on the intake manifold near cylinder 1... common problem is the intake manifold gasket leaks vacuum causing a misfire...the not starting could be due to a faulty crank sensor