Okay, first, I understand one can expect to lose power on the lower end of RPM range, from posts I've seen. However... I counted ("one one-thousand, two one thousand", etc) in my head this morning, and it took me a full 16 seconds to get to 60 mph from a dead stop. UGH. I honestly by no means expect that I am sensitive enough to be able to tell with certainty every 5 hp gain, but this seems like a pretty substantial step backwards.

My expectation was that the catalytic converters in the manifold went bad due to a code that popped up, can't remember, but seemed like the consensus was that it was a cat. I took a while deciding what to do, and then one morning it ended up barely going 20 mph from being clogged so bad, and so I pulled over and had it towed home so I could work on it. I decided to put a header on, because it was far less expensive than repairing back to stock, and secondary was the small power and potential mpg gain. When I was changing it out, I took the Y-pipe out and shook out and tried to vacuum and use an air hose to blow out all the broken pieces of the converter guts that had blown back from the converters in the manifold into the stock Y-pipe cat. I figured this cat wouldn't be too bad, because it's not getting anything until after the first two already filter most of the stuff out.

When I took the O2 sensor out of the Y-pipe, I noticed the threading was screwed up. Has anyone else had this? It was so badly crossthreaded, that when I went to put the O2 sensor back in, it was simply impossible. wouldn't start, and there was only about a thread or two left on it from when it was installed originally I suppose, and so I just unplugged the thing and put a plug in the hole from the header that came with it. My expectation is that since this sensor is after the catalytic converters, it wouldn't be seeing what it expected anyway.

As for the other O2 sensors, I just put them back in. Seems like someone said the first one is the only one that matters because it gives feedback to the system for A/F ratio stuff, but I assume when people say "the one" in the front, they mean "the ones" in the front, because (if I remember right, this has been a few weeks) there is an O2 sensor in front of each of the two converters on the manifold. If these two are first and second, then the third is immediately after one of these converters, and the fourth/last one is the one on the Y-pipe. I put the first three back in as usual.

So...
Any suggestions? I'm not really interested in putting in a new Y-pipe and exhaust system if that's not really necessary. Could I just drop the Y-pipe and jam a screwdriver through the inside of the third cat? vacuum it out and move on? Will the fourth O2 sensor being unplugged and removed cause big problems?

No worries on exhaust inspections, there's no smog inspection or anything here in Kentucky. I just want it to be stock or better.

Also, side note, might thread separately on this, but there is a website that makes exhaust gaskets that are supposed to be really good. They don't make them for this application but I emailed them and they said if I had an old gasket I could send them, they would quote doing a batch. The website is here if you guys want to check it out..http://www.remflex.com/

 

The 02 sensors must be plugged in the format it suppose to be.

 

Even though the signal will be different, since the cats are gone?

If this is the case, anyone know what the thread is in the Y-pipe? I will need to get a thread chaser or something to recut the thread to get the O2 sensor back in there.

 

You would need to add a test pipe on each bank and put the 02 sensor in the correct area.

 

I recommend reading this page for a short and sweet O2 tutorial:
http://www.aa1car.com/library/o2sensor.htm

The first O2 sensor (the one closest to the exhaust manifold) is very important as it adjusts your air/fuel mixture. The other sensor(s) (down stream) after that one are for emissions purposes to make sure your cat converter(s) is/are working properly. If you have removed your cat converter, you need to fool the ECU into thinking that the downstream O2 sensor(s) are working properly so you don't trigger the CEL. Google "O2 simulator" for various options on how to trick the ECU. There are electronic ones that you splice into the O2 signal wire to send the correct voltage signal back to the ECU. There is a mechanical option too but my guess would be that the mechanical solution would not be as reliable as the electronic solution to fool the ECU. Perhaps if you have disconnected some of your sensors the car has gone into some sort of fail-safe mode that is limiting your performance. (Just a wild *** guess.)

This link will give you some info on a mechanical option:
http://forums.clubrsx.com/showthread.php?t=296791

This link will give you some info a electronic version:
http://www.mkiv.com/techarticles/oxy...sor_simulator/

I have not tried either so do so at your own risk. Good luck and report back how it turns out!