Thanks for your responses again, Jason.
The hg will be a project one day. However you mentioned a clogged muffler. After I read that, I later went outside and whacked the muffler several times with my hand while it was running, then I covered up the pipe a couple times just to put some back pressure on the system. Then I got in and it ran great! I drove it about 20 mins that night and drove it again the next day with no problems, so... it's fixed.
I guess it really was just a clog somewhere. Thanks again! I never thought to look at something at the back that seemed to a problem in the engine.