Here's something I wanted to try for fun... My stock manifold onmy 1.7 SOHC has really tiny holes and what look like sleeves.... I thought of taking a Die Grinder and smoothing out the flow that goes into it. It's just something to try in my spare time... sort of a "Hey, I wonder what would happen if" sort of deal. I have researched it a little and from what I found... an aftermarket Cat will only yield a possible gain of a whopping 1HP (this information comes from my buddy's 93 Accord Sedan with an H22A swap done: he has the laptop set up in the car and we measured it using both the Chrome and Uberdata programs before and after. so I think it's fair to say that spending money on a supposed "High-Flow" Cat is a big waste especially in my application. So with that said, before I go and grind this thing can anyone forsee any error codes popping up? I'll re-iterate that I only want to try grinding the inlet ports of the stock manifold. The manifold had the 2 O2 sensors (one before and one after) That's why it's such a pain in my ass to find an aftermarket CAT at a non-rape price point I appreciate any and all input.