i'm thinking of changing my cat back piping to 2.5" from the 2.25" i have at the moment. i have a header, 2.75" (i think) flexi and high flow cat, just wondering if i'd see any gains from this??

on a side note- i have came gears and i am about to get a whole lot of tuning done. my line of thinking is that i should probably sort out all the bolt on stuff before tuning.... tuning is about 3 months down the track though.

am i right??
or wrong?

TIA

 

Your header has a 2.75" collector?! Woah....that's huge...

 

Yes, change the piping to 2.5 inches. If you're going to boost, you'd want a three inch b-pipe. Dont forget to upgrade your cat too and you're set.

 

no plans for turbo (insurance goes out the window in this country with FI cars, you can hide NA mods from inspectors though). the cat is already a high flow unit... is there something better??
don't say no cat coz it's a $10k fine here for no cat.