The fuel is fairly new. I believe it falls within your time frame. I've used it my other lawn mower and it works fine.
I've removed the gas tank and cleaned it out. I have also cleaned the carborator. New spark plug. checked the muffler and after taking if off, I blew air through it. It's the orginial, and I can't remember how old the mower is.
I was thinking of the 3 things the engine needs, fuel, a spark and air....
You got that right. As long as compression is in the mix too...
If you're surging, that's usually either a weak or deformed governor spring or a plugged carburetor. That a late 2005 engine, probably on an '06 mower. Has the carburetor ever been rebuilt?
Yes, you can get them at an local Briggs dealer. Here's a parts illustration: