I'm not sure about the coils-me thinks that when you have a coil going south, that would send a code to the computer telling you that you have a miss in that cylinder. Do you have a scan tool to reset a code if it's thrown?
If you have a scan tool to reset everything I would try unhooking the mas while the car is off-then crank her up-if she runs ok,you'll know that the car is in limp home mode and that the mas was the culprit.
You could still have good brakes with a vacuum leak by the way-the line to the brake booster is seperate and it would only take a little vac leak to cause you to lose power. I have had this happen and not throw a code. I agree with you-don't start throwing money at new parts but check what you have then make your move. Another part that could give some problem though would be the knock sensors-might try reading up on them-there's good write up about them in the faq's.
Also on tyhe back of the fuel rail is a hookup that you can get a reading of your fuel pressure-if your fuel pump is going down it could give you the same type of power loss your experencing-just noodling along here
Poolman