Which thing gives more power header or cat-back?? My euro-spec ITR has the stock 4-2-1 style header and a test pipe. So do you think I will gain more by fitting a 4-1 header OR a cat-back exhaust? Thanks guys!

 

Header, but you'll be much more satisfied if you do some exhaust work at the same time.

 

Work from the inside out.

 

The best is to do both, but start with the header and remove the first bottleneck of the stock B-pipe. You need an 2.5" testpipe/cat too....
The stock euro header is shitz....

 

Header all the way.

 

Both.....But header 1st....don't make my mistake...

 

What is the first bottle neck ??

 

This one... between the b-Pipe and CAT.

 

So if I do I test pipe will it be ok?

I orderded the DC JDM 4-1 will I need any special hardware to fit it except a test pipe with a 2.5 inch flange??

 

both at the same time, but if you like feeling the gains of each mod(i am one of these people), header first.

 

Check this: https://honda-tech.com/zerothread?id=204632

 

I ordered the same header last week.
I already have a new 2.5 flange. I´ll post pics next week.
It´s not easy to find a 2.5 flange for your stock cat.

 

I'm selling my spoon header, 2.5" collector, $700 odo, let me know

Nick