[Mr.Impreza]

Originally Posted by Ashikabi

It will matter. There is a thread on here for/by the HKS rep, I'd find it and ask him. I think his name is Tony or Torry

Found it, thanks man!

The calibrations supplied in the Flash Editor (and the dyno results) were generated using the required HKS Spark Plugs, HKS Stainless Exhaust Manifold, HKS Stainless Center Pipe, and HKS Hi-Power Spec-L exhaust. I'm confident a comparable header/manifold will still work with the pre-loaded calibrations however, the degree of difference in performance vs. the HKS manifold will be the degree of difference in driveability and output. Of course you can always have one of our Pro-Dealers tweak or create a custom cal. for you.