If you really want power gains for your car kaya ka nagpapaheaders, I'd suggest getting a "branded" headers for your ride.

Complete with test results pa...

Kung ricey headers effect lang naman ang plan mo, I'd suggest stainless, madrel bent pipes na 4-2-1.

I heard Mufflerland have mandrel benders (but I haven't tried their product and I don't know where it is exactly located - marami raw branch ito, like tomas morato).

HTH