After trying almost everything, I put a new SRAM 8spd chain on and voila! Perfect shifting. The old chain was only 25% worn. I was ready to swap out the chai rings, but fortunately that wasn't necessary. I then returned the bb to the unusual L and R orientation, whereby the drive side is shorter than the left side. Who am I to doubt the campy mtb gods? It may also be of interest that the spacers between the middle and granny ring give a slightly larger space than middle and big. (I hadn't explicitly said it before but I'm talking about a mtb triple. I know, I should get my own thread... Sorry)

Long story short: got a new chain and riding happy.

Ciao tutti.