Wassup guys? just joined the speed 3 family not too long ago, i bought a 2011 speed 3 and i love it! its exactly what i was hoping it would be. I have an injen CAI on it and HKS bov i am looking in getting a full exhaust system & down pipe, need some suggestions which way i should go ? also plan on getting the AP, is it true i should change the fuel pump on it first?

Kinda new to this forum thing, just felt like doing something different so i joined it.

 

WTF is "AP".
Generally speaking with exhaust systems, you should not go any bigger than 1/2" above stock, 1/4" is what I did (from 2.25" to 2.5") and am very pleased (for my Mazda 6 3.0 ltr). Find out what size most aftermarket cat backs and stick to that. Any bigger would be hurting performance as per: MagnaFlow Performance Exhaust - FAQ, Frequently Asked Questions . Change your rear main cat (the one that don't have O2 sensors on it) to a larger diameter hi flow one like from Magnaflow or something. Changing this rear cat will increase your flow.
Unfortunately you'll have to do some figuring from the dealer. Mazda usually offers catbacks, ask them if it's bigger than stock diameter and what those dimensions are. Use this to figure out your main rear cat size and get a universal one from Magnaflow custom installed.

I would also seriously consider a Water?methanol injection kit. For basics, READ: https://www.mazdaforum.com/forum/nit...-turbos-30333/