As long as you don't over size the ID too much, you should be fine.

 

Come on exhaust guys, chime in here please....i got mufflers sitting in my cart and need to know what is the best to do.

 

Let's get back to back pressure.

Back pressure is an issue for an engine that can not adjust fuel delivery.

Now I'm not entirely up to date on what all the computer on our trucks can change on the fly, but if they can adjust fuel delivery, you shouldn't have a back pressure issue.

not enough back pressure used to burn up exhaust valves, but the fuel mixture wasn't being changed in those cases.

Ultimatly, it's your truck. If you want 2.5" or 3", then it's your choice. Maybe someone else can discuss fuel mixture.

 

OK so here is what it looks like under my truck....now im not sure if i can even do this as it seems that the cat is right right up against the factory y.



I think this cat but correct me if im wrong.



This is the 3in pipe from (what i think is) the cat that goes into my flow master....i have a 3in SI - 2.5 DO.

 

Ah, 1 cat and it's after the Y pipe, which in this case is Y mid pipe (as it travels from the manifolds to the Cat) Bummer. So true dual won't be cheap as I thought, due to the O2 sensor and needing another cat.

Based on this set up, you system is ideal as is without spending a bunch of cash.

At this point I would consider a performance CAT and a different muffler if you want new sound. Which brings us back to the "Y" pipe in the original post.

New CAT, "Y"pipe and 2 mufflers or New CAT and a new muffler with DO?

 

I intend to run LT's on my RCSB so in preparation I mounted a Magaflow SI/DO muffler as far rearward has I could. I used a Magnaflow "HiFlow Cat" directly in front of the muffler. The cat is now just above the cross member giving enough room for the headers and "Y" pipe. I ran the stock OEM cat for a short while waiting for the Magnaflow Cat to be delivered. When the HiFlow was installed I slowed a couple tenths with my 0-60 mph runs telling me the OEM cat flowed better than the Magnaflow "HiFlow" cat. When I do the LT's I'll re-install the OEM cat. I recommend you have a extra O2 bung welded into the system just in case you decide to install a A/F meter. I did mine backassward as I modified the previous exhuast system to fit my roll pan and found it to be unusable and didn't have time to do the headers.

 

So your saying get the y pipe and a new cat? how would that run if i want duals....would it be new y into the new cat then to another y then to the muffler?

 

Wow it actually was worse....how does that happen?

 

I'm saying if you want true duels you might need 2 CATS.

Otherwise:

engine=>cat<=mufflers=tips

 

Gotcha...thanks