My first post!

I have searched through the FAQ and I think my issue may be a bit different than what I've seen addressed here. But forgive me if this is a redundant question.

Some months ago, in an attempt to get my car running smoothly and quietly, I had an ATP 101122 "high flow" manifold/cat installed to replace the broken factory mancat. I am reluctant to simply pull the part off and go with a header and y8 setup for a few reasons: for starters, I paid about $450 for the part and labor; second, I understand it would be easiest to avoid a CEL if I leave the O2 sensors exactly where they are now; third, I'm concerned about losing velocity with a header since I don't plan on doing much with the engine itself (I only have CAI, maybe some tuning later) until I swap out for a B18C in a couple of years, and then it will be a whole new exhaust system anyway. But the rub is that I'm convinced I currently have back pressure because of the skinny factory midpipe which is still part of my exhaust system.

This car is Daily Driven, btw, and it needs to be reasonable at low RPM (stop/go traffic) as well as reliable and easily maintained. Oh yeah, and Arizona is no pushover when it comes to emissions inspections. We have them yearly.

Will it make a difference if I customize the manifold exit to fit bigger piping? Has anyone done this to get better flow? Ideally, I want to have 2 or 2.25" coming out after the cat and therefore a true "catback" system.

Any advice is greatly appreciated, so thank you in advance!

 

if you have a d16y7 header, then get a DX/LX catback exhaust system and it should bolt right up to the header since the cat is in the header/manifold itself. If it's a high flow manifold, then you don't need to modify it at all, just bolt on a catback and you'll be set. 2.25" would give you some power and be about perfect for your N/A application. If you were planning on boosting in the future i'd say go a little bigger than 2.25", but i think thats about perfect for N/A. 2" is too small to spend that much money on it, and 2.5" would be okay too but you might lose a little bit more torque than you did with the 2.25"

 

Thanks for your response, Flip.

I've been thinking about my setup and maybe I will swap out the manifold for a Magnaflow header/cat if they make one that has a 2.25" exit. I could always sell the one I have used on ebay for $150. I'm going to drive the car with this exhaust for about 2 years so it would be worth it.

I'm pretty sure the high flow man/cat I have is OEM (Which is 1.75", right?). That's why the midpipe is so skinny, it fits exactly to the man/cat exit. It's like this choke point or bottle neck in my exhaust that I want to get rid of. I might end up swapping for a Magnaflow in the end. Do you think it would be worth it? Do you know if they make a 2.25" exit header/cat? Maybe I could pay them $1000 to make a custom one!