warm start problems
What are you gear changes like? There is usually a vacuum connection to a modulator in the box, and if that line is damaged/broken, or the modulator in the box is leaking, you have an air leak. This should cause some hard shifts, so you should have noticed it. The way it starts running high then slows down may point to a softened/cracked hose that leaks briefly, then shuts as it is distorted by vacuum. Maybe the extra air valve is misbehaving? Any other strange things happening?