header and catbacknce i already have an aem cai

im installing my obx header and skunk2 catback tomorrow, at the same time. what kind of differences am i gonna notice in terms of power, since i alredy have an aem cai on there? do all three of them work together to make more power than any one of them by itself?

It'll be quite good.

Yeah, I had the exact same situatuion.  After my header and cat back was put on I noticed a nice gain

would the fact that my engine may not be in tune hinder the performance of the gain id get from those 3 combined mods? it needs a valve job and every thing else they do at 100,000 miles.

Eh, well either way you'll feel a gain unless your engine has been thrashed to no end.