Won’t idle after new muffler

Just don't tighten them too much, itll distort the body potentially crack the ears off.

Probably just coincidental that your carb needs to be re gasketed , float inspected needle & seat replaced AKA rebuilt.

If it were the muffler ...it would be one of two symptoms, from one of two causes. First one... it would idle lower if the muffler had no back pressure and was put in place where a stock Style Muffler was used before....or B the other way around and the idle goes up to 1200rpm. Lol

Vac leak...and "Do I have a vacuum leak" should be the title of this thread.

Jmo