The threads on the cat studs rusted off and so I'm left with the option of welding the pipe to my age old cat of unknown usefulness or just running a test pipe. Anyone here run a test pipe on stock ECU? I know it will throw a code but will it affect performance or MPG? What's better putting the o2 in a bung in the pipe or just strapping it to the outside of the pipe?

Berz out.

 

it will throw a CEL but wont affect drive-ability , another way to bypass it is to buy a 02 sensor extender plug it all in and no CEL.. its the secondary 02 sensor behind the CAT that you need to put a extension on 02 Oxygen Sensor Extender Spacer Extension M 18 x1 5 HHO Bung 1 75" Longusa Made | eBay

not specifically that exact one. find one that fit a honda thats just for reference

 

Test pipe installed and here's my thoughts on it.

1. The V is now Quieter than it was with the cat installed. I am guessing I had a small leak from the rusted bolts for awhile that was allowing more noise than I thought. Now it's all being funneled out the tail pipe and the stock muffler is great. I was actually hoping for more sound than I got though.
2. I notice an increase in power for sure. I'm guessing the stock cat was far beyond it's useful time on a vehicle and was probably restrictive.
3. No CEL .... yet. I've got the O2 strapped to the sway bar for now.

Berz out.

 

there are 2 02 sensors front of cat and rear of cat, by having the front 02 removed your car will eventually waste gas because the ecu is not getting the 2 value it needs to do fuel trim, and throw your car into limp mode with the CEL , one being the 02 sensor isnt being heated once the ECU runs through the monitors , but the 2nd 02 will throw a code and your car wont go into limp mode