Unless You're having fuel-vapor/boiling in the carb issues, just make sure the flap is working correctly. I believe some have made a "block-off" plate out of stainless sheet, but cold weather warm-up performance may suffer.
I'm likely gonna drill the busted bolts and put a blocking plate in there. The flap is frozen so if I can't get it to work I'm just gonna plate it off. The stock muffler is rotted so I'm probably going to run a glass pack or two.
And yes, I'm trying to keep this as budget as possible. This is my first car and I naturally don't have much money to play with