I would definitely do Art pipes if I was in your position. They will take an hour or so to remove and replace with stock cats for emissions versus many many hours and a complex installation process for long tube headers. From least amount of power to most amount of power, this is what I think:

stock cats < high flow cats < test pipes < Art pipes < LTHs.

Or for torque:

Stock cats < test pipes < high flow cats < Art pipes < LTHs

However, you have to realize that the difference between Art pipes and LTHs will be a few wheel horsepower at most.

Exactly. That is the primary reason for putting the HFC on the XYZ pipe.

Secondly, it makes more power by moving the HFC away from the engine.

Thirdly, it greatly increases the life expectancy of the HFC because exhaust gas temperature is about 300'F-500'F lower at the end of the merge collector.

BTW just ordered the ART pipes today, and just got a message saying they will ship today. Great service!

I did read what you said.... I SAID that ART PIPES with Stillens... I didn't say just other set-ups... ART pipes are PROVEN to put out higher gains than your standard test pipes or HFC's.... so unless this specific set-up has been done under the same conditions then it's speculation... thank you.

all you're doing is trying to put a plug in to sell your LTH's.. why are you selling them if they put out such good gains exactly?

Plug for my headers, I was not the one who mentioned my sale. People can find them in the FS thread on their own if they want them.
Why I am changing? I have a SC and they work fantastically, but I am moving towards something more than just gains as I always have. Balance is key with my car, now just in weight or power but also sound and style. It all has to work together to achieve what I want. Power is only a small percentage of what one can do to a car.

Speculation is what makes it all go around. ART pipes I am sure show better gains on some setups and less on others. It is like I have seen other products do the same thing, every car, dyno, day is different and you must take each result posted at that value for that setup.

that's all well and good... my point is simply that as far as I know back to back LTH's vs ART pipes with Stillen headers have not been compared.

all great suggestions guys. Wish had the money and time to do all comparisions but leaning towards Stock/Stillen header plus ART.

I can understand that. It would actually be a big project to do such a comparison and its not exactly something most people would have the time for.

I'll leave this open to anyone interested in doing such a comparison. It would make a valuable comparative data point for the community.

What are you currently using in the location for the stock cats? Stock cats, HFC's or test pipes?

agree there... but headers will probably be the last mod I do... it's going to be to install the ART pipes, and then buy and install the XYZ pipe and then get a CBE. Then intakes... Perhaps Tony you all may have your intake finished or close to it?

By the way Tony, I was wondering... if I don't want a loud exhaust... and since the ART pipes obviously are not a hfc... would I be better with the XYZ with HFC or resonated? I guess resonated since I could always put my OE cats back on right?

Intake comes after the exhaust. As far as HFC Vs resonator on the XYZ pipe... I would suggest the HFC. HFC because it will at least clean up the smell. For some people this is important.

The smell of test pipes or ART pipes doesn't bother me at all but it is an issue for some. It depends a lot on your personal preference and smog regulations.

any idea of power gain on resonated vs hfc?

The XYZ HFC drops 3-4 HP relative to the XYZ resonator or XYZ straight pipe.
Normally a HFC would drop more than 3-4 HP relative to a test pipe but the XYZ HFC is so much farther away from the engine there is less pressure drop and power loss.