Why engine keeps backfiring when accelerating/ going uphill?

What is your question?

For a few months now, every time I start accelerating about 30mph, the van seems like it is backfiring/not wanting to accelerate. Once you get up to speed, it continually jerks, not terribly hard, but it does it. I noticed my muffler is really loud. Could needing a new muffler cause the van to do this?