http://forums.nasioc.com/forums/show...hreadid=447182

Good read

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Mazda CX-7
Mitsubishi Evo X MR

You are probably thinking of this one from hitech:
http://www.perth-wrx.com/vb/mechanicals/11923-hitech-turbo-back-exhaust.html

As I mentioned in that thread there is no hard evidence to support the claims of the company. They are just trying to sell you their product.

There are some good test results on the aps website though to support my claims of reducing in back pressure:
http://www.airpowersystems.com.au/us...wrx-hoe-r2.htm

its common in well built jappy exhaust systems that they step diameters between 3.5-3-2.5, as the exhaust pulse changes shape, it drastically reduces the noise/drone without hurting the power.

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Long live the WRC

PM sent

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No more GC8, sad face.
[SIGPIC][/SIGPIC]

Reading the APS site there is no back pressure difference between the R2 (3" to 2.5" diff back) and the R1 (full 3") with a cat fitted. With no cat the readings start to differ from 325hp up.

interesting articles...thx for infos, also i found out the HKS hi-power is 3" catback for the GC8 models so it will be 3" from tbe if i get a xforce dump(rip of hks pretty much). The 3.5" are for nissians coz of their inline six.

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STi Version VI

Is the diff back section 2.5"? It doesn't seem to mention it anywhere....

Turbo to Tip Systems





Click here for details
P/N APSWRX-HOE/R1


Click here for details
P/N APSWRX-HOE/R2
^
^It tapers down to 2.5" just before the back flange of the center pipe.
Click here for details
P/N APSWRX-HOE/R8