I have a Poulan Pro snowblower with a 8.5hp Tecumseh. I was out using it, and had run it about 20 min. Suddenly, it started surging badly, just like it was running out of gas. I stopped and checked, and it wasn't empty, but I filled it anyway. When I started it, the surging stopped, but it ran rough. Applying a little choke seems to make it run a tad better, but the difference is small. Between that, and filling it with gas stopping the surging, I'm inclined to think it's fuel-related, but wanted to check with the experts. Again, it ran fine, and the problem started suddenly. Thanks!