Update: I took it into a shop a while back and had it checked out. It turns out I had a couple of bent valves that would occasionally stick and bang up against the piston. They ended up sending my heads to a machine shop and overhauling them. It was a bigger job than I would have been comfortable doing myself so I'm glad I took it in. She runs like a dream again and I'm hoping to get at least another 150k out of her!