In article , oldjag wrote:
Some metal content, (barely)...This started last spring actually when
I helped a driver in an '69 olds 442 convertable that died on the
roadside. Towed the car to my home garage a block away.
[...]
I'm sure you simply omitted to mention it, but I didn't see any indication in
your post that the spark plugs were replaced...

One other thing, kind of a long shot, but I've seen it happen befo when the
other shop finished with the rebuild, did they get the plug wires back on
properly? Incorrect firing order would easily account for the idle being
worse, and power way down.