Lewis7789

Alright guys, I'm a little puzzled by my motor here. I have a 92 CX hatch with the puny D15B8 (I'll be getting a B20 in the winter, don't worry) I bought a DC 4-1 header, Ebay high flow cat (basically a resonator), and an Apex Dunk cat back exhaust. The stock cat is in the header along with the O2 sensor. I replaced the stock header with the DC, re-routed the O2 sensor for the DC header and installed the new cat.
Problem is it would sputter while cruising in third and fourth gear around 35mph with about 1800 rpm. The motor was running very rich, leaving black residue on my back bumper and it would bog when the motor got hot.
I installed a new O2 sensor and it didn't fix it. So I re-installed the stock header/cat combo and it runs just fine again. I'm trying to pick up a cat from an Si to replace the highflow cat to see if it helps. I've been told there is no such thing as not enough back pressure, but I'm still not really sold on that idea...
Has anyone every heard of this? Any ideas on how I can the DC header without it running like poo.
Again, I'm getting a B20 in the winter, so you don't need to razz me about the little D15B8. I'm well aware I have 90 hp with the bolt-on's.

Thanks guys!

Lewis7789

Anyone? I've heard Honda-Tech is the place to ask specific questions and that you guys know your ****.