need help with header and cutout setup and sizing

ive decided to go with kooks headers with the kooks y-pipe and qtp's QTEC. I need help deciding what size header i should get. I want the the qtec to still work with my stock catback. so it'll go headers, y-pipe, qtec, cats, catback. with the headers there are some with venturi collectors. wtf is that? some have only O2 sensors and some have both. ummmmmmmm :uhoh: how do i choose? and then theres all these different sizes like 1 3/4" x 1 7/8" x 3 1/2" and 1 7/8" x 3" and 1 7/8" x 2" x 3 1/2". What does all this mean?! :confused:

also, what would i weld the qtec into? the y-pipe?

Cats need to be a few inches off the headers.

What year car?? What motor?

02 firehawk

1 3/4" headers, you don't need (or really want) any more than that unless you are pushing 500+ RWHP.
3" pipe
3" cutout(s), one right after the y-pipe, or one right before each cat. (second option requires custom work)
3" cats, which need to be 6-8 inches from the collector of each header.

how bout the egr and o2 and venturi and air fitting/collector options?

and also the y-pipe setup? do i want catted, or cats or no cats or w/e? i dont know

Do you have to pass emissions??

yeah, i guess. does it make any difference in performance that i have to? how easy would it be if i didnt have to pass but all of a sudden i do. like, how difficult would it be to return to stock setup or a setup that would make me pass emissions.

Well, emissions is something that can be changed with a set of headers.
EGR you don't have.
AIR you do. If you were to get race headers, you would have to have the codes removed for the air pump. Also, it depends on what kind of emissions you might need to pass. Sniffer? Visual? ODB? It all depends.

Headers....I run race headers. No EGR or AIR hook-ups. I will figure out what to do about emissions when I need to. I know it won't pass, so......

Any difference in performance??? Probably not.

what if i skip the cutout and just have open headers. i know ill gain a lot of hp but will i lose a lot of torque?

Probably won't gain anything with open headers. I lost power. More low end torque than HP, but I think it lost some HP as well.

Sounds like you want it to perform well, and be loud.
I would recommend a single cutout after the y-pipe. Then run stock cat-back beyond that. You will want 1 3/4" headers and 3" y-pipe though.

so i would have to cutoff the end of the ypipe to weld the cutout in, right? also, do you know how difficult it is to install kooks headers? i heard on some headers you have to take off the motor mounts and rock the engine back and forth to get it in.

Installing any headers on an LS1 car isn't easy.

Be patient is all I can tell you. Sometimes some of the heat guards have to be cut as well. Good luck!