Flow thru catco, or stock?

I have a rs type flow thru catco (no mesh), and the feedback from a friend was that it makes the check engine light come on.(the 02 sensor downstream says its to rich of a mixture)he says his car runs better....idk

I wanna know if installing this on my car a good aftermarket mod, or a waste of time.

what kind of car?

95 eclipse(DD)
The exhaust Sys consist of Dc Headers(wrapped),stock catco, and a rs type tip but still has the stock pipes.

The other car ,with the same type of catco already installed, but diffrient bolt pattern, is a Honda hatchback like the one in your logo.(Non Turbo, with a B series engine) I dont know anything about honda swaps but I wanna say I heard him tell me a B18.. or 16, not sure though.

Im trying to get feedback on what I wanna do. But some of the people ive asked in waco either dont know what im talking about or give me a speech about the gases that come out the block, but I simply reply by telling them if people were worried about the enviorment these diesel trucks would have a better way of getting rid of their exhaust instead of leaving behind a huge cloud of black smoke.

so far what I got is

1. Because it dosent have a mesh, or filter, to slow down the gases from leaving the block it speeds up the process so it can create more waste meaning more HP(supposivly)since the faster it can get rid of it the faster in can make it.(more combustion)

2. Too much free flow will make you loose HP, exhaust gases are deadly, since the ecm or ecu is reading too rich of a fuel mixture, I was told it might make the car run like shit.

Yeah if you want HP gains or a noticeable difference, you might want to do more than a cat. at most that will change the sound of your car.

oh well of course im well aware of that im not the kind of person that sticks an apexi tip on the car and thinks I got some more horsepower...lol. I have some bolt on mods on the engine, but im trying to "upgrade" on my exhaust performance. You know how when you change one thing on a car you have to something else, thats what im running into at the moment. I do however have a 8lbs turbo thats meant for my engine and base model but I do not have the fuel pump, fuel injectors or any type of tuning device for it. but im not worried about HP right now just performance, gas mileage and my tires. I just wana know if letting my exhaust gases flow freely a good thing or a bad thing since it dosent have to go thru a mesh

I say no because the money you waste on it, probably won't do you any good and if you are going turbo, just do a test pipe since Waco doesnt have emissions. Well 3" test pipe/exhaust when you turbo...

what he said