Well, that depends on whether the engine really needs the exhaust system to be unclogged or not. Without knowing the engine and the size of the stock system, and all sorts of other stuff, it is hard to say. There are some vehicles where merely replacing the catalytic converter with a straight-pipe (and no other exhaust changes) actually reduced HP and Torque slightly, as the exhaust system already had optimal flow characteristics for those engines. Of course, if you have done engine work (cams, port polishing, intake mods, forced induction) then the exhaust system may no longer be optimal. When I replaced the exhaust system of my old Toyota with a 2-inch cat-back, I gained a little oomph in the higher RPMs (more peak HP), but my low-end grunt was lessened and I lost ~2 MPG. On the other hand, a temporary repair I did on my Honda Civic that choked the exhaust down to 1-1/2" just before the muffler made my throttle response a little sluggish, but I still got the low-end grunt (not that Hondas have much!). I lost a little high-RPM HP, but I don't often go over 5000 RPM in daily driving. The biggest thing is that my MPG went from 23 to 28! (Yes, there ARE Civics with poor MPG ratings. 4WD Wagons w/ ATs are the heaviest Civic ever made and have the most drivetrain losses.)

Well I'm not a Certified Mechanic but a retired telecommunications tech but I have spent 50 odd years under a shadetree. Are you wanting to replace your Cat Converter and muffler with a straight pipe from exhaust manifold to rear bumper?Improve ..I think so but not wise.I once had a motorcycle that sometimes the muffler would fall off and it would almost jump out from under me. But, it Wont pass inspection and excessive noise tickets for sure...

Being a certified mechanic, it is of course illegal to cut out your cats. However, it does improve horsepower, low end torque, and gives your exhaust just the sound your looking for. It completely gives your exhaust a large opening, being that the the faster the exhaust is expelled from the motor, the better it will be. From my experience, I would do it.

Back in the day when that piece of s--- cat con came out they was still trying to grt the gas right, people were still useing reg lead gas, it was like real cheap back then but it would plug a cat up in a year easy! And you better bring the bank with you for a new one!!! So what we did was cut the cat off we would cut just in front and just in back of it. Take a piece just a little bigger and put that in place of the cat---(it's called a test tube) BUT you have to do it yourself or find someone that will do it on the QT. There are not many that will do it anymore! (the Law) and don't do naything to the muffler just the cat. It will even run a little better.

i dont know.