Why does my truck chug a little?

I have a 1987 ford bronco 2 v6 I cut the exhaust out and just put a short pipe in the cat I replaced the fuel pump cause it was bad and the starter my q is it chugs sometimes i don't know if my fuel gauge is off or if it's not getting back pressure from the straight pipe i don't know a good answer will be awesome thanks.

Chugging a little is good. Hey if you put a shorter pipe now there's less backblow so maybe it is running LEANER so check condition of plugs, maybe need richer mixture to compensate and if you add more fuel ya need more air, too. If ya heve no runnin road ya need to be reading da plugs