alright guys i have decided to make a thread about this cause i feel not enough people will see it and chime in if i post it on the exhaust sticky thread. so basically i have an exhaust leak i think i've pin pointed it out it's after the headers before the precats. i bought some 5zigen fireball mega's and am going the custom route for this.

from the engine it's going to be stock headers - stock pre cats - 2.5 in piping (single) all the way down - deleting the 3rd cat or resonator - still 2.5 in Y pipes - all the way to my 5zigen axle backs. all 304 stainless steel. i was quoted $250 for materials another $200-$300 for labor in all around $500-$600

wanted to know everyone opinion on this set up, if someone already has it please chime in how is it. is it possible to delete the precats and just put one high flow cat before the 2.5in Y pipe? would that be better?

any suggestions would be great won't be getting the steel for 2-3 days so im trying to come up with the best set up as of right now. i do want to go NA-T in the near future so i did decided to stick with the 2.5in piping until then.

 

A diagram would make it much easier to follow but from what I'm understanding...

You have a leak somewhere between the upper cats and header, but are not addressing this at all? Instead you are replacing everything downstream?

A 2.5" single is sufficient but if you DO plan for FI in the future, why not just do 3" single to 2.5" duals and 5zigen axlebacks. It's better for NA and also unquestionably superior when you boost.

In terms of cats, I say the less you have the better off you are. If you MUST have a cat, I would say put a single Magnaflow 3" in the midpipe. The upper precats are only useful for cold start emissions and do next to nothing good once the main cat heats up anyway.

 

im sorry if i confused anyone with my mediocre diagram

with the exhaust leak between the upper cats and headers i am going to address that, im sorry i did not state that in beginning looks like there's just a gap in between both of them causing the leak.

how is this?
( from engine ) - stock headers - 1 magnaflow 91005 2.5in/out high flow cat - 2.5 piping all the way to the 2.5in Y pipe - 2.5in piping all the way to my 5zigen axle backs - ( rear of the car )

i hope that made more sense to you folks and would love some more feedback on this.

 

Wow, thats alot. My 3 inch exhaust only cost me 180 bucks. Straight piped tho.

 

i would say if you do a Y pipe i would reduce the size or you wiill lose some low end torque. aparently you already have the 2.5inch mufflers so i would go 3 inch from the headers to the y pipe and 2.5 after the y pipe. like somone has already mentioned in an earlyer post. even if your not planning on boosting this will still produce more low end torque in an NA motor then 2.5 all the way down.

ALSO i would save money on the magnaflow high flow cat and instead get a catco high flow cat because they perform just as good and are half the money. THEN i would use the money that you saved and get a performance y pipe because the y pipe will be the most restrictive part of your exhaust so i would make sure that is addressed.