More cam could mean extra strain on already marginal valve springs. This could explain some of your problems but you should eliminate electrical and fuel possibilities first before jumping to mechanical solutions.
If the thing was nosing over at the top end, thats a classic case of valve float...............you never mentioned spring pressure or how old they are/were.
I also agree that it may be a tuning issue but I don't feel that changing the cam all of a sudden makes the plugs any better or worse than they were before..............
Is this a vacumm secondary or mechanical? You may have a slight vacumm loss (based on overlap) and thus not bringing in your power valve or secondaries early enough............
