[Perfectlap]

m97 engine on trickle charger for 9 months...hmmm. You should make a habit of driving it at least on short trips more often. Things can dry out and you want to burn off that build up, for this you want to drive it long enough for the oil to come up to temp. I think that seems like a bigger issue than your spark plugs. To protect these engines you have to drive them at least once in a while.

spark plugs are cheap. Why not.