The tegiwa header (toda rep) really look nice compared to other replicas. The quality also look better. The only bad thing about this header is that (from dyno test : http://www.tegiwaimports.com/pdfuplo...old%20test.pdf) it will only gives little whp compared to other replicas. Is that because the collector on the tegiwa is 2 3/8 compared to 2 1/2 on other replica?

 

A lot of factors go into determining how much hp you get and how much hp you can gain by adding a particular header.

Collector size is a factor, but so is the length, diameter, and merge order of the header. Complicating things is the fact that some headers will be best for some builds but not for others, because the headers, exhaust, intake, cams, etc. work as a complete system and maximizing power comes from properly configuring the system, not just lego-building by adding components because they did well on someone else's build.

A better way to go about things is to ask:

1) Where is a Toda replica going to make power compared to other headers you're considering
2) What header best complements your build
3) What headers meet your criteria for radiator clearance, ground clearance, cat compatibilty, etc.