Seeing that 5 as it starts to sputter still tells me acc pump issue. The power valve may also be sticking or just crap as well. If you have the means to test it I would, otherwise I'd just replace it with another rated at 5.5. Each of these circuits are responsible for supplying your engine with extra fuel during low vacuum/ high power operation. That 5.5 rating would insure that it was opening as your engine is starting to lean out. My bet is that you'll find your bog there.
Oh, David; "vacuum."
