When Luke finally collapses in the snow, he lets out a grunt as he lands on his face. No grunt in 70mm; No grunt in 85PS; No grunt in 93; grunt is in SE

Yoda makes a frightened "Ehhhhh!" sound just before Luke says "Like we're being watched" and points his blaster at him. No frightened "Ehhhh!" in 70mm: not in 85PS; not in 93; "Ehhhh!" is in SE

I can faintly hear the face-fall grunt in the pre-SE mixes.

There's also the grunting as he tries to free his feet from the ice in the Wampa cave and the lightsaber deactivation sound effect, which are mixed much lower in the pre-SE mixes.

The grunting as he falls down the carbon-freezing steps may have been added for the SE, however, since I don't hear it in the earlier mixes (although I haven't heard the 70mm).

Also, Yoda's "Ehhhh!" was there at some point before the SE. I have an old VHS tape with a recorded 1980 tv review of the movie, and a clip from that scene shown during the review features the "Ehhhh!"