So I am planning on putting in a boost actuated cutout from Sound Performance as well as a catalytic converter on my new build. As you can imagine I am planning on having the cat post cutout but if I go too far I am afraid that the cat will never light off and just be a restrictions.

(1) What size is the factory exhaust, 60mm?
(2) Has anyone placed a 3" cutout in the test pipe and had plenty of room?
(3) If I put the cat just beyond the factory house flange will it get hot enough to light off?
(4) Should I get the 2.5" or 3" Cutout?

 

Well you have an inline pro kit with a 3 inch downpipe don't you? Why would you want to put a 2.5inch bottleneck in there?

 

agreed. after seeing what joey just did, 3" FTW

 

Should have mentioned that I have a 2.5" DP now, but those details will come later.

 

You NEED the 2.75!
Phil had one....

 

I added a 3" magnaflow cat to my set up and really lost no power. I actually made more power with a AEM, Intake and CAt over the Emanage no intake and no cat.

 

If I put in a cat it will be 3" and I will use reducers basck to 2.5"

 

OK, why?

 

Why #1 - To increase the cross sectional area to effectively lower the resistance.

Why #2 - The plan will be run a low boost (Wife) tune with the cutout closed and a high boost with the cutout open. This will allow her to run 10-12PSI on low boost and make good power still.

Why #3 - As Trbokev tells me I like to make things more complicated then they have to be.

 

As I thought, I did the 5 inch Random Technologies cat necked down thinking the same thing. FYI, it didn't last 80 miles and totally plugged the exhaust system costing power and a big chunk of money. Now it is a funny looking test pipe.