Upon inspecting the model, here's what I think. It appears that there many have been a constriction on the fuel tank tubes as they passed through the hole in the firewall. Minor shifting then starved the engine for fuel. So I enlarged the hole, reinstalled everything and will give it another shot. If this isn't it, I'm all out of solutions.

I also added a guide tube for the driver that I use to adjust the hex bolt in the end of the needle valve. I had one already but it was too big and the driver couldn't find the nut when the engine was running. Doing it this way is more of a hassle than just having a wire extension (or the old trick of using a small allen wrench) but I wanted to try this out since that's what I'm doing on my more serious scale models, where it's not ok to have a wire sticking out the side of the model.

Of course, there's not gurantee that this is the problem on the Puppeteer as well, but it at least gives me a place to look.