Hi Karash!
I haven't noticed anything strange with my 84 since my little AH break; it still seems one of the most stable planes in the game. I do, however, fly with stall limiter.
My guess is that it has something to do with your stick settings. Maybe the sensitivity is set too high, and the plane isn't liking (what it sees as) aggressive control input?
Oh, and I never bothered with the trim thing either. As far as I am aware, you'll get the same effect just pulling back all the way on the stick. Plus, it's one more thing to worry about in the middle of a fight, which is never good.