The pellets kept going out? Think it was those particular pellets or does the AMZNPS struggle in that smoker? Just wandering cause I have a MES 40" and am looking at getting the AMZNPS.
Just as some woods are more dense that others, that wood used to make the pellet is also more dense. Some woods are harder to start and maintain without experience. But folks here will readily help you figure out which is which. Then you can mix with less dense woods to make a better easier to use smoke.
Personally I don't use anything but chips in my chip tray. Pellets in the pellet tray and dust in the dust tubes. Flare ups or flashes can be dangerous. I can physically shoot the chip loader out the side of my smoker with improper usage. Course I had to do it 3 or 4 times to make sure I knew what was going on. LOL <evil grin>
Pellets need a slightly greater air flow than the designed chip tray. I can't get both to work harmonious but each on its on is fine.
The AMPs will work great in that MES40, it does in mine. Although if you plan on a pellet convertion might I suggest you use the search engine and consider a Mailbox modification. It's fast, its inexpensive, and it seems to be the answer most are looking for. I might also suggest you look at the dust tubes/trays They require even less are flow and I don't believe I have ever heard a problem mentioned with them. They can even do cold smokes.
Hope that helps you.