How Restrictive Is The Stock Muffler On A 5 Hp Briggs Flathead ?

#1
Hello-it's been a while since I last posted.
I have a 5 hp Briggs flattie that was made in the 90's. I am going to put a 22mm slide type carb on it. Can I still use the stock muffler, or should I put on a header? Using the stock muffler would make life easier. The muffler is the box-type with 2 bolt holes in the corner.
Thanks for any info.
 
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