|Leaking brake booster normally creates a hissing sound. Its normal for the RPMS to drop slightly when you press the brakes, how big a drop we talking?
Your symptoms are kinda all over the place.
Ignition timing is ok, MAF is ok, you really need to confirm fuel pressure next.
Then I'd go rent or buy a vacuum gauge from the store. They're very simple to use and there are many easy to understand how to's to read them. Hook it up to the balance tube. It will tell you a lot.
Have you checked your codes?