Anyone have any real knowledge when it comes to the build quality between these guys for engine modifications? I know some of them outsource/rebrand already, but I'm kinda curious as to why there is such a price discrepancy between the different companies for similar parts. (i.e., pully/headers/ecu/throttle body).

Why is it that Kleeman is significantly less inexpensive than the likes of the others? Why is Brabus power so much pricier given the lesser reported horsepower numbers?

I realize that marketing has a lot to do with it, I'm just curious where the real "product quality" differences do apply.