While I haven't dyno'ed the car, I have noticed an insane increase in power. The car feels completely new. I have all Ebay Headers, Secondary Pipes (catless), Custom U Bend's and a "Beluga Racing" Muffler from Ebay. The sound is the most orgasmic thing I've heard in a very long time. With the full exhaust there is virtually no drone in all RPM Bands, With just the Muffler there is reasonable drone around 2k to 3k but the exhaust gets quiet after a while and in higher rpm.
I started with Headers, Then Muffler. But the real change in the way it all sounded was completing it with the Secondary Pipes without cats. I do have to pass emissions tests but thats fine as long as the car is running good with no check engine lights. And my O2's without the extenders read mildly ok. My O2's however are sometimes throwing the "old o2" code. which is claiming they are dying so they will be replaced here soon after I do emissions to re register my 986 in a week.
I was planning on building my own exhaust because the cost of a "race exhaust" or any exhaust if you made it yourself, would cost a ton cheaper than purchasing some name brand overpriced piece of metal. NO Exhaust should cost thousands of dollars for the short length of a Porsche.
But I just said screw it, bought the ebay parts since they will only be on the car for another year or so before I swap the motor.
The car has lots more low end torque, Front end lifts up pretty high if I slam the gas at low speeds.
I wish I could take a video of the sound but I'm all alone right now. I do have a video of just the headers and muffler but the sound changed a lot (for the better) when I did the test pipes. I honestly say its a very nice exhaust.
I also couldn't find any U Pipes that were the right size for the new exhaust, since the new exhaust is much larger in size. All the aftermarket U Pipes I found were the same size as stock. So I made my own out of some Flex Pipe for now.
Muffler 299 Shipped
Test Pipes 160 Shipped
U Pipes 25 Local
Headers 113 Shipped.
So for 600 dollars you have a really awesome sounding full exhaust system that will give you some gains, now if you have the ability to tune or have someone tune it, I'd do this also for additional gains. DO NOT Just install a muffler, you're not doing anything but making the exhaust a little louder. The real issues in performance is the stock Headers and Cats. Their design and pipe diameter is a HUGE restriction.
Headers
Test Pipes (Secondaries)
Muffler