I thought of another thing... renal artery stenosis.

This however would be more of a constant elevation and not
likely such a swing.

Now, dopamine is a heart stimulant. It is used when people have heart attacks and strokes sometimes. Injectable dopamine.

First ask yourself if you had these spells BEFORE the ACE inhibitor use. If so were they this bad, or lighter?
What was happening to me happened within 2 hrs of taking my dose for the day. Once it was absorbed orally it blasted me.
Since I took my lisinopril at night, this meant I woke up in pain, and burning and generally a mess. When I started to swell up all over...couldn't bend my legs arms, back, I became frightened. There are GI symptoms with bradykinin, of pain, and bloating, and the breathing problems. I was huffing and puffing like I needed to blow of "steam" or something.

Pheochromocytoma, is displaced adrenal tissue that is congenital. The spells of hypertension, will happen when there is any stimulus --sometimes just compression of the mass by bending over. They are small and do not show visibly for the most part or hidden in the adrenals themselves. They are found diagnostically by a test where a dye or tracer is injected and a body scan then done.

Here is an article:
http://en.wikipedia.org/wiki/Pheochromocytoma
Pay attention to the foods... if you avoid those foods, see if you
have fewer spells of the really elevated pressures.

If you can find a nephrologist or endocrinolgist to see, and evaluate you, that would be best I think.