Problem vehicle is 85 244 with 324,000 miles - automatic transmission

I replaced all of my vacuum lines yesterday and now it seems that the cruise control is a bit over-responsive/bouncy
when going down a hill it surges and lets off, surges and lets off
when it surges, it does so longer and more often than it had before the vacuum line replacement - but, the surges are softer than the small number of strong, but short in duration surging i had experienced before

what seems to a be a completely seperate issue is speedometer squirrliness
the speedometer had been bouncing around recently so i pulled and checked my cable
the outer casing had been cracked and slightly bent at the place it mounts under the body 18 inches from the tranny end, i pulled the inner cable out and it was not bent nor rusty, but not shiny either, so i put a hose clamp and thin rubber around the cracked casing
when i put it back in i packed the sheath with grease
now it operates very smooth and steady until i have driven about 15 miles then it sporadically bounces, as well as sporadically indicating 5-10 miles under the speed i am going (estimated based on engine revs and feel)

but, the cruise squirrlyness and speedometer squirrliness sometimes co-exist
this seems to be a red herrring, as, from what i know, they are not inter-connected on this more archaic system

My thought is that the improved vacuum needs to be accomodated by reducing the cruise module's sensitivity

BTW - i will be replacing the speedometer cable with a new one when it is delivered in a few days.

Please sirs, and ma'ams, provide commentary and insight into this situation.
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rich - '85 244DL with 323k