Another thought for you -
Use one of those cheap IR temp pistols to check the cylinders and exhaust pipes. You know the kind, they usually have a red laser pointer on them. Maybe $25, most likely less. We'll call it the Poor Man's Engine Analyzer!
You can take some live readings while the engine is running. More than any particular temp, you're looking for DIFFERENCES between the cylinders.
Measure cylinder #2 (the suspect) with both mags AND L/R ONLY! You want three sets of data. Knowing what happens on L/R mag only is very helpful in diagnosis.
Measure the exhaust temp about 1" below the cylinder head. Measure the spark plugs, measure the heads. You'll quickly notice any cylinder that's "out of whack", and you'll have a good basis for determining the cause.
EDIT: Here is one for under $25:
Etekcity Lasergrip 1080 Non-Contact Digital Laser Infrared Thermometer Temperature Gun -58℉~1022℉ (-50℃～550℃), Yellow and Black
by Amazon.com
Learn more:
https://smile.amazon.com/dp/B00DMI63..._kmq7FbZP5ZR8C