99-06 Headers on NNBS
 

I know the 99-06 LT headers will fit on our NNBS trucks but I was wondering if you guys had to replace the cats when you put the new headers in or if they just bolted right up into place? Let me know guys, hoping to get some ordered in the next month or so and just need to see what I'm up against.

You will have to relocate the cats futher down but I will go with out cats if I was you

+1 you would have to have the cats put into the ory if you want to keep them. No big difference in power with or without but for most it's a emissions legal Issue.

The way my exhaust is ran right now I'm not sure how much farther down I can go with the cats without redoing the exhaust, any suggestions? I would just run it straight but here in CA emissions is a MOFO. If I ran without the cats would I expect any issues as far as computer sensors are concerned or anything? Also would I be looking at a little extra gain or loss without them? And my last question on that would be sound, without the cats am I going to hear a throatier exhaust because of the less restriction?

yes it will throw a code. just get a catted y-pipe to go with the headers

So the 99-06 pacesetters will fit the NNBS but is that the same for the 4WD also?

There are a couple things you can do about the code it will throw. You can buy a couple of spoofs, which plug into your O2 harness. They simulate a working O2 sensor, so your computer doesn't know that you took the cats out. Or you can buy HP Tuners software, and really go to town programming your pcm for not only additional power, but tire changes, gear changes, etc. Oh, and you can even turn off codes like the one that is put out when you remove the cars. :)

Where can I buy spoofs at and how exactly do they work? Again first I've heard of anything like that, would have helped me a lot on my last truck with smog!

I'm assuming the O2 sensors are the same for most all GM vehicles. That could be a bad assumption. I used these on my 2002 Camaro SS for a while until I got LS1edit.

http://www.afterthoughtsauto.com/o2sim.html

Thanks jaywoo I'm going to shoot them an email and make sure it will work for the NNBS trucks and if so then I'll just do my LT's with no cats and use the spoofs.