The cruise control on my 1993 945T works okay, I guess, but it surges, most noticeably on upgrades. I only use it on the interstate, so they are gradual upgrades, but still I get the surging. It holds speed well, but the tach will show an increase in revs, the boost gauge will get a little into the boost area, and I can feel a fairly abrupt acceleration, followed by deceleration, followed by acceleration.... you get the picture.

Is this normal? Or is it indicative of a problem with the cruise, or some other area?

I can only compare it to the cruise on my old '89 Mazda, which worked flawlessly.