I just got my Infiniti G35, and I was thinking about some possible mods. The gas mileage is kind of ****, but it's a fast car so if there is no way to increase that, it doesn't matter.
About the exhaust system, I was wondering if it would be possible to get a longer set of aftter market headers, connect the Y-tube directly to the headers, then attach ONE catalytic converter behind the Y-tube instead of having two cats. Is this possible?

 

Anything is possible with enough money and a shop that will do custom fabrication. Depending on the cell count, a single cat may throw a code. Wires will probably need to get extended and another o2 bung added to the cat.

This should be in the exhaust section.

 

Do you know how much that would cost me? I know a place that would make a custom exhaust for $600, but I don't want to do anything that'll mess with the cars reliability

 

Nope

 

Ebay or Stock and I highly recommend you pick the latter but have a feeling you will do the exact opposite. Enjoy the vehicle and what you plan to turn it into

 

Wait I don't get it, what will I do with Ebay? There isn't much I can do about welding without a machine? Where are the O2 sensors at in this car?

 

There's 2 sensors in the cats and 2 somewhere near the engine.

 

So can't I just put one into the single cat? Do people who get high flow cats just place the o2 sensors in the new one?

 

And leave the other sensor disconnected??? No you can't do that since both rear sensors will need to be hooked up. HFC's have o2 bungs just like OEM.

 

is there any cats with 2 places for an o2 sensor? What about a custom cat?

 

You could make the single cat work, if you're willing to get a Uprev Osiris tune and have to codes for the secondary o2 sensors disabled, then just have bungs welded some where in the exhaust for emissions.

 

Is that expensive?

 

Probably set you back around $7-800 with $600 of that going to the tune.

 

Hello,
What type of exhaust system were you thinking about going with? Are you thinking about doing an entire custom exhaust?

What are your overall goals with the car? Are you planning to tune that car as you will need to in order to get the full potential out of long tube headers.

Just seeing if I can help you out with some of your decisions.

 

You could go with PPE long tube headers (eliminates the cats and connects right to the y-pipe) and then run something like a motordyne y-pipe with single cat module off of that.

The PPEs ain't cheap, and neither is the Y-pipe / Cat combo from MD though. You're gonna be running over $1500 for that if you get a sick deal used.