Well, this went very well and then very badly.
Replaced all the tensioner components, and in the process replaced the water pump (it seemed a little grindy in turning) and the vacuum pump. Started up and everything was smooth as glass. No shaking or bouncing and no noise.
I don't really know what happened. I was on the first test drive out about five miles and back. It sounded and felt just like I ran over a rock, but I saw nothing in the road. Then the belt started flapping around a little bit, then worse. I pulled over and popped the hood - belt was gone, tensioner was sitting sideways somewhat, and the belt had snagged the lower transmission fluid cooler hose and snapped it in two. Jumped in and got another 1/10 mile to a service station and then got towed home.
I really thought maybe the tensioner lever bolt had come out. I used a sealant on it and torqued it properly. Unfortunately the bolt was fine, but the timing cover has broken where the tensioner is mounted.
So I gave up for today, maybe I'll see what caused all this tomorrow. It was really smooth and running great. I suppose the earlier bouncing around stressed the timing cover and cracked it - but that seems a bit of a stretch.
Have a feeling the cover will be quite expensive.
Ken300D