I have a 93 yota pickup standard cab with 3.0 and 5 speed manual trans. When I bought it the previous owner had cut the cat out and welded a pipe in its place and he also cut the muffler out and piped it as well and split the pipe from where the muffler was to the bumper (y pipe). It sounded like a pissed off bumble bee on steroids so I immediately took it to a muffler shop and had them install a muffler. I told the guy I wanted as close to stock sound as I could get without paying high dollar for a new cat. He welded a muffler before the split in the pipe (the muffler looks like a 55 gallon barrel). It sounds amazingly quieter than what it did when I bought it so I was happy. However, I pull a 14 ft single axle trailer with a 72" cut diesel zero turn mower (weighs about 2500lbs). The truck pulls it ok but it bogs down considerably going over an overpass (yes I am down shifting). Would a cat help with adding more torque or is it even worth it to try considering how big the muffler is? Any help would be great.

 

Unfortunately, they don't call this motor the 3 point slow for nothing. Maybe a bigger factor here is your tire/ gear combo. For instance, my 4runner is a factory 4.10 geared vehicle, and I have 31s on it. While it seems to cruise a little better at freeway speeds (lower rpm) on flat ground, it definitely struggles noticeably in the hills. If you are running anything bigger than the stock tires on the factory gears (assuming they are 4.10s and not 4.56) you might really be facing a gearing problem opposed to a muffler problem. Don't know what gears you have? Heres a chart that may help you.

http://www.off-road.com/trucks-4x4/t...ion-18588.html

best of luck!