I would just change all the fluids, adjust valves, sync throttle bodies, etc. and ride the crap out of it. It's been sitting a long time, and you may just have some sticking rings. Some Marvel Mystery oil in the gas (upper cylinder lubricant) can't hurt.
I see this sort of thing all the time in airplanes that sit a lot. No need for surgery, yet. Check back after a few hundred miles.. if it is still acting up, it's time for a leak down compression test to see what is going on.