Was out on the water this weekend.

Had a problem with the drive-trim so made the 70-mile run with the drive trimmed down the entire way. Most every time we took a bit of air, the boat seems to loose its stability and began a gentle, but increasing chimewalk. Simply throttling back would restore full control.

After pulling the boat (Baja 272 w 502 EFI) out of the water, noticed "quite a bit" of play in the sterndrive (Bravo/1 w 23p MP). Seemed like about 3-6" of play before the steering wheel would move.

Isn't there an adjustment to tighten up the drive and reduce the amout of "play"?

If you get in the boat and look at the transom you will see the strg arm that comes in from the drive. Have someone move the drive and see if the arm moves. If it doesn't then the pivot and arm are worn and will need to be replaced-very common.

What happened to your engine problem

Still being worked on by Mario (SoCal Speed & Marine).
Went for an island run on my son's (Chrisf) Baja 272 on Saturday.

Also look at the pivot pins where the bell housing rides in the gimble ring. There are bushings that may be worn and need to be replaced.