Ix9

I’m not familiar with pellet stoves, but would a converter work so you can reuse the old exhaust pipe in place?

https://www.homedepot.com/p/Master-Flow-7-in-to-4-in-Round-Reducer-R7X4/202191795

Same here. I know a lot of folks don't like the results, but to be honest, I don't find Google any better these days.