I have a 2.8l 89 RS with a Dynomax dual exhaust. It's been on there for a while, and recently one of the tailpipes rusted to the point where it was hanging down and I had to just tear it off. This has been hurting my backpressure, and a friend of mine had a suggestion which would do me one better than just replacing the muffler.
He said I should put a catalytic converter on after removing its guts, then cut the pipe off after that point. My state does not have vehicle inspections, so even though this would be sick loud and highly polluting, I could get clean away with it, and I'm told it would produce a 25% increase in horsepower (probably an exaggeration, but any increase is always welcome ).

He said he did this on his 2.2l S-10 and was able to beat any V6 Mustang off the line.

So, if anyone has any other ideas on how much this job would do for me, and any advice/links on how to do the procedure would rock.

 

You are not "hurting your backpressure." For our applications, there is no such action capable. Extremely high performance four-strokes, which isn't even the type of "backpressure" you are thinking of, and mild to wild two-strokes can be hurt by insufficiently tuned exhaust channels - specifically two-strokes

If you have no visual inspection, or emissions inspection, than you will most certainly be ticketed by a police officer.

If you are going to gut the cat, and you don't need to pretend you have a functioning unit, then cut the pipe going to the manifold before the cat. Hm.

Tell your friend I am royalled shmoozed by his comparison with the wicked-fast, Mustang. That reminds me of everytime I go by some r1ce-mobile and see v6 advertised. That is darn ridiculous that the v6 is an option. A pitty.