so im trying to make my monte a true dually but i just bought a flowmaster exhaust catback. since i only have 1 cat can i jus cut the piping and add another cat an reconnect the pipes or would that not work? also if i was to remove the original cat and replace it would it throw my check engine on light? feel free to be as explanitory as u want. any advice would work.
thanks

 

When I went from single exhaust to true duals on my 93 F150 I removed the stock cat and replaced it with 2 high flow cats. You have an O2 sensor before the cat correct? Thats how it was on my F150. I made a small H pipe where the duals were the closest and relocated my O2 sensor into the H pipe so it was getting a mix of exhaust gasses from both banks. Then I ran the cats after the H pipe. I never had any problems with throwing a CEL and it truck ran great afterward so I guess it was working quite well. Thats what I would recommend doing.

 

True duals means the exhaust stays separated from the headers all the way to the x-pipe, right?

 

Yes, true duals have 1 exhaust pipe for each bank of the engine all the way to the tail pipes. Alot of "dual exhaust" RWD cars and trucks, have a y pipe up front connecting the exhaust from each bank into one and then another y pipe out back separating it again into 2 tail pipes. Making a true dual exhaust eliminates any convergence into one pipe and freeing up flow as well as changing the exhaust note.

 

OP maybe these photos will give you some ideas. I had to run both pipes down the passenger side because of the fuel tank, but you may have more room to work with under your monte than I had.



Here is where I mounted my O2 sensor


Cats side by side


Mufflers out behind the cats


You can use your imagination here. Obviously you will need to route yours differently but the concept is the same.