Not quite done typing for the night, haha. Regarding the manifold, I am going to relay one of Teds suggestions that has worked beautifully on two of my motors and a number of my friends'.
His recommendation, at least for the sub 5k rpm world we are in, is to keep the stock manifold. It is already basically a header. Then run 2" pipe from the down tube (or whatever it's called that connects to the manifold, still a factory Toyota part), then step up to a 2.25 high flow cat, to a 2.25 magnaflow or other true straight flow muffler.
This is a high flow setup and you get the advantage of that manifold which is QUIET. At least compared to the DT or an LCE that sound like you have little chirping birds under your hood.
On the older motors, that downtube (collector? Idk what the part is called) actually remains two separate tubes for like 2 feet, essentially giving you a tri-y header.
Anyway, if you are going to do a high flow catback, why not weld it up to the stock manifold and see how it goes? Might save yourself $400. Those headers sure do look purdy tho, haha.
