Is there anyone here running a 5zigen Fireball cat-back?

I have one on my UK ITR, and was wondering if anyone had dyno'd with theirs fitted?

I have just obtained a JDM ITR header for my ITR, what will I need to do to mate it up to the 5zigen?
Custom Decat/b pipe?
What will happen when I mate up a 2.5" b pipe to the smaller 5zigen pipe?
Would I be better off getting rid of it and getting a 2.5" system?

Sorry if this is two questions in one

 

i dynoed with my 5zigen fireball. i got 189/127

i also have a jdm 4-1 with a 2.5 test pipe, it bolted up fine, but it's an obvious bottle neck. i'm getting a custom 2.5 catback this week, fyi.

 

Thanks for that

Was that the only Mod on your car? that seems very high ? I take it that was WHP?

I think eventually I will go for the 2.5" cat-back, but for now I should still gain with a JDM manifold and the 5zigen? How many WHP gain would you guess for the JDM manifold? (Its just the OEM honda one) not a uprated one.

 

This thread shows gains from JDM manifold and carsound cat.
https://honda-tech.com/zerothread?id=300031