Okay, So I have an HKS Hi-Power dual exhaust on MY00 I have been lurking around for a while trying to find a good header and test pipe to mate it with.

From all I have read the 3 inch is the way to go, followed by a single 70mm and so on.
Great im already behind as my HKS is only 60mm.

Most of the headers I find have a 2.5 inch collector or 63.xx mm.

I understand you dont want to have the bottleneck on your exhaust, but using a 2.5 inch collector header with a 60mm exhaust I do end up with one, as my collector is larger than the rest of the system.

Should I just get a header with the 2.5 inch collector and a 60mm test pipe? Or would it be a better idea to just replace the whole thing?

I know that Toda, J's Racing and Tracy Sports all make a header that have a 60mm collector. The price is a bit steep for me, but If its what I will make power with i'm okay with spending the money.

Should I get one of those headers and a 60mm test pipe?

Will I loose any power from running a 2.5 inch collector header vs a 60mm collector header?

 

Toda or J's headers with 60mm tp with your HKS dual.

 

remember that you're talking about outer diameteres.
inner diameters are theones which matters.

i would go for "usual" headers - IMO that 2.5mm difference is nothing and larger header is better.

 

A header with larger piping is only possibly better if you have just as big or bigger piping after it. Going from 2.5" collector down to 60mm is just silly. If you had a proper plan, you'd avoid situation's like this(believe me, I've been there).