i've considered most of those. but the grande ran strong until i messed w/ it ... so i'm guessing that i can narrow it down. i'm familiar w/ the dellorto (and other than the size, it was essentially the same as a 14.12 or similar model) and so i'm pretty sure i put it all back together properly.
i'm thinking it might be that the carb is not on tight enough, so that it has air leaking. i'll take it all out (again!) and fiddle w/ it some more next time i have time and it's a nicer day out.
i'm thinking that maybe i'll need to figure out a way to make sure the carb is tight on the manifold ... that might be the culprit.
oy! ... but i'll keep working ...