Good points about the air filter. You need as much air as you can get.
The Rochester B and BC models are notorious for having two problems not associated with air filters, however...warped castings (which can and do cause vacuum loss) and the power piston becoming stuck in the bore by virtue of ethanol laced gasoline. Actually some will say any unleaded gas will contribute to sticking of the piston, but the main thing to understand is when that power piston fails due to vacuum loss or because it is stuck, it is always stuck in the "down" position...meaning it leaves the power valve open. And this causes the carburetor to run too rich all the time. Hopefully you don't have that problem, but it is possible. If you look at the very top of this section, you'll see a tutorial I wrote (Straightening the Rochester B and BC Castings) about how to straighten the castings using a common gas bbq grill and a simple piece of flat metal and 4 nuts and bolts. I also wrote a companion report which I need to re-write detailing the common Rochester B problems...the image hosting service for those images sort of had some trouble so there are no images now.
Your fuel additive (depending on what it is) may help. Probably will help, actually. As I said, friends over there complain to me about not having ethanol-free alternatives.
