[brainsboy]

You have something wrong with the 770. You said its running too rich. When you go with a carb thats bigger then what you need the air flow through the carb gets slower, this causes lean conditions not rich, so something is wrong with your carb. After you jetted down you noticed it bogged because your already lean and now your going even leaner then before. The first thing I would check in the 770 is the power valve. Sounds like it's leaking or opening up on you.

As far as the 15" of vacuum that seems way off for your setup and camshaft.