Your carb guy is feeding you a bunch of BS. Adjusting the floats won't hurt the needle seats, that's what they're designed to do. If you only have two threads showing your floats are low in the bowl. You can pull the needle seats all the way out and blow out with compressed air to remove any dirt and then screw them back in. Your Edelbrock intake won't cause your problem unless it has a vacuum leak somewhere. Now, your vacuum, the vacuum will drop just a little when applying the brakes but it should rebound almost immediately. If it drops and stays low you have a leak somewhere in the brake booster or vacuum hose going to it.