After some major surgery the Bonneville is back on the road and running smooth as silk again! The long and short of it is that when replacing the UIM, I found the LIM gaskets were beyond shot and definitely had a vacuum leak from the gaskets. I replaced the LIM gaskets with the GM aluminum LIM gaskets and also had to replace a weak fuel pump.
While I was in there I did a massive clean up as 170,000+ miles caused some accumulation of the nasty black stuff, so I cleaned the throttle body, the LIM and did some spot cleaning of the valves and engine since everything was apart.
The end result is a Bonne that'* purring like a kitten and is ready for another 170,000
Thanks again for all your assistance. A couple of business trips got in the way of getting the job done, but the work is done and old reliable is reliable once again!