That's definitely a head scratcher, Seasick, as there's many possibilities. And, you're right, things don't usually fix themselves. The one thing that stands out, to me, is that you said "just added stabil". Now, from that statement alone, it sounds like you may not always use it or you added a healthy extra dose of it. If that's the case, I might think that something could have been slightly fouled. The extra dose of stabil sitting on it all Winter ate away at the fouling and it burned off while you did your Spring pre-run. I've had experience with heavy doses of stabil doing just that with small engines that were running a little off. At least... that's the only variable that I see from what you wrote. I guess just give a good run and see what happens.