I have an '06 goat that I got a couple months ago and put 2 chamber flowmasters on it and took out the resignator. It's sound really mean but at high RPM's I can still hear the restriction coming from the cats. I know if I take them out it will set of the check engine light. Is there a place I can get mill eliminators to shut the light off? What about having the cpu reconfigured so the o2 sensors don't set it off?! Will taking the cats out help my performance at all or will it reduce the back pressure too much and make the motor not run right?! I have a 55 chevy that I rebuilt with a big block so I know a lot more about old school power where running open headers makes it go the fastest. My knowledge lacks a little bit when it comes to the computer systems. Any reply would be greatly appreciated..

Taking the cats out will help get you a little more performance. However, I personally would not touch them until I put on a set of long tube headers. At that time you can either go with an offroad pipe (catless) or midpipes with high-fow cats. In my mind, either option is better than stock, with the offroad pipes giving a little more performance. Overall, I think you will be all right in terms of backpressure. After all, you do still have the Flowmasters on the car.

You can have the rear O2 sensors turned off if you have your car professionally tuned. Either that or you can pick up a handheld tuner, Diablo Sport Predator, and turn the sensors off yourself. You can get such a handheld tuner from someplace like Marylandspeed.com.

-K

Well, lets start with costs....

OEM Cats 800-1000 minimum (not something that you want to ruin)

Tune (to shut off the MIL) 500 to 900

Next, the cat back on these is very restrictive, and flow masters aren't the best choice for power, but do sound good

cats take maybe 15-20 HP from the engine, not a ton. Aftermarket ones a bit less.

If you don't mind spending money to get power, go with Kooks LT Headers, (cats or no cats, it's up to you) and a cat back system that isn't pinched down like the OE parts.

Either way, your going to need a tune to get the lights off, even if you go with the Kooks with the cats, your light will still turn on.

cats take maybe 15-20 HP from the engine, not a ton. Aftermarket ones a bit less.
How much additional horspower would you suspect one would get if one swapped Kooks high-flow cats to offroad pipes?

Either way, your going to need a tune to get the lights off, even if you go with the Kooks with the cats, your light will still turn on.
True! It happens to the best of us. It is because of this that I had my rear O2 sensors turned off when the car was tuned for the first time.

-K

With the hi flow cats, they probly take 10hp compared to without, not a lot.

If I am not mistaken, you can turn off the rear 02's (eliminates CEL with no cats) with a predator. I bought a used one for $100. The cats on my car are not long for the world. lol.

Perfect... Thanks a lot.. I probably will just leave the cats on until I decide to put full length headers on it. I already set off enough car alarms. I just hate hearing how restricted the exhaust sounds at high RPM's... I have another question about induction. I've looked at the aftermarket intakes and I really don't like where the filters are. Has anyone done anything in either trying to make the hood scoops functional or making a kit that puts the filter closer to the ground allowing colder air?! Or is there currently a kit that I am not finding?

First off the stock catback system on the GTO is not very restrictive. I wouldn't even bother upgrading it for additional power as you will only get about 10 engine HP...read the results from Borla and other manufacturers, they don't give alot of gains because the muffler isn't trying to make the exhaust as quiet as possible.

As for intakes your pretty much stuck, there are a few kits here and there to make the scoops functional but I wouldn't bother using one, your best bet is a CAI.

The predator alone (non SLP version) can't remove the codes, but you can ask Diablo to do a custom tune thing and have that done, but it takes a bit.

Nocturn, have you looked at the rear pipes on the 05-06's at one point it crushes down to half size.

The predator alone (non SLP version) can't remove the codes, but you can ask Diablo to do a custom tune thing and have that done, but it takes a bit.

My car is an '04, perhaps that's where the difference lies...but I am almost 100% certain I can turn off the codes for the rear 02's with my predator.

The predator alone (non SLP version) can't remove the codes, but you can ask Diablo to do a custom tune thing and have that done, but it takes a bit.

Nocturn, have you looked at the rear pipes on the 05-06's at one point it crushes down to half size.

I was under the impression that one could turn off the rear O2 sensors using the Predator. Perhaps I am wrong. However, I cannot find a list of the complete set of features on the Diablo website.

My passenger-side pipe before the muffler was crimped, but I was surprised at how unrestricted the pipes appeared overall.

-K

I was under the impression that one could turn off the rear O2 sensors using the Predator. Perhaps I am wrong. However, I cannot find a list of the complete set of features on the Diablo website.

My passenger-side pipe before the muffler was crimped, but I was surprised at how unrestricted the pipes appeared overall.

-K

No, you can erase the code, but not delete the code from happening. This must be done by Diablo themselves. But it can be done, just not with what you buy. This is true on the 05-06, i'm not sure about the 04.

Overall the pipes looked very good, but there is a section between the resonator and muffler that crimps down to half size.

No, you can erase the code, but not delete the code from happening. This must be done by Diablo themselves. But it can be done, just not with what you buy. This is true on the 05-06, i'm not sure about the 04.

Well, that sucks. I guess it was a good thing that I did not go ahead and pick up a Predator after I had my Kooks installed and threw a code. I would have been highly upset if I were not able to turn off the rear O2 sensors after having spent $400.

Overall the pipes looked very good, but there is a section between the resonator and muffler that crimps down to half size.

Yeah, we are talking about the same crimp. I just don't remember it being severe. I will have to take a look at the stock pipes again to refresh my memory. I guess that the memory really is the first to go with age. ;)

-K

I havn't given it a details inspection, but the fact that the aftermarket companies can't get more than 10RWHP out of a set of new pipes for 600 bucks is enough to convince me. The tail pipes don't need 3" of pipe anyways as the exhaust has suffeciently cooled by that point.