I run dual 2 1/4" pipes from manifold to tips, the only mufflers I run are "cherry bombs"(you can see right through them). No cat.s, & no air pump. I change the plugs once a year(before aircare) and make sure your engine is running hot. I kill the electric fan when in the line-up, turn it on around 210/220. Haven't failed yet.
Cat.s suck ass, they filter exhaust by collecting the carbon, then they get clogged, get real hot, and all the collected carbons start burnin-up. thats Y they stink when they are shot(or so I've heard).
If your truck runs smooth I'ld just do it. Then if you do fail, it'll tell you why. Go from there.
Good luck to ya.
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BroncoIII