We have had the X for a few weeks, and in that amount of time, we have dynoed the car in stock form, and dynoed the car with a custom hardwired Unichip. Both have proven to show very good HP numbers, and this is with the stock exhaust, intake and other parts! Like our other builds we have done, we are building the parts for this car in the direction that we expect most customers to build their car. So after we were done with our ECU tuning, the first item we built is the Catback Exhaust.

The formula for the catback is simple. 3", Stainless steel, mandrel bends, and a free flowing muffler that is quiet. Using a similar design to the stock muffler, where the center inlet and dual outlets exit the sides, we started with the back of the car. With our basic muffler laid out and 4" tips in the back of our mind, we started... The 3" center inlet muffler consists of a standard straight through type muffler, but with a center chamber that divides the exhaust pressure equally to both sides. The look of the tips is very important as the OEM tips are horrible. They seem crooked, not quite the right shape, and not fitting of the back of the car. The STI at least provides tips that fit the back of the car. Its like Mitsu forgot about tips and made it a last minute decision. We went with 4" tips, and just for fun we bead blasted the tips to provide a dull silver finish. This may not be how the production tips look, but it does provide a very clean look. The tips are lined up to match the fins at the back........ Please ignore the dirty car.......... With the catback exhaust done, the next part to replace is the catpipe. Like many other guys out there that would replace this with a catless pipe, we are not going to follow that path. Like we have been doing over the last few years is strive to make more legal parts for your cars. The catalyst on the New EVO not just one cat stuck between 2 flanges like the old catpipe. The new cat pipe has 2 bricks in it, and one 02 sensor. While it looks like it's just one, there are 2 cats in the same pipe. Here you can see the 02 sensor wire harness/bracket........... One, in front of the 02 sensor, and the second behind the 02 sensor. So in order to keep the system legal like our other parts, we had to make the cat pipe with 2 cats. I know everyone in the EVO world is saying there is no way that it will make power. We have been using the dual cat setups on the Subaru's for a while now, we have seen virtually ZERO effect on overall HP. Even on cars making 400WHP or more, 2 cats doesn't seem to be an issue. In the pics you can see the strange bracket that is bolted to the bottom of the pipe. This is the bracket that takes the 02 sensor wire from the passenger side of the car, to the driver's side where it plugs into the cat. OEM vs. PERRIN Prototype, ours is lighter, neener neener neener............ Next up on the exhaust is the downpipe. This part was very hard to build on the car, so instead of fighting the tight spaces, I made fixture of the OEM part. In order to ensure the PERRIN downpipe wasn't going to hit any other parts on the car, i measured the OD of the OEM pipe and added room as though it was a 3" pipe. Some assembly required............... Close up of OEM part and the PERRIN 3" Downpipe...... Here you can see the studs for the heat sheild........ On the fixture I used some welding rods to mark the tight areas and the centerline of the pipe. I would show a pic of the fixture, but it was kind of ugly. All the extra work paid off, as the finished part fit perfect on the car and had no issues with clearance. Like the OEM part, we made sure to put the heat shields on the downpipe next to where it passes by the rear driveshaft output. Looking up at the heat sheild..... One more lookint up toward the turbo.......... After all said and done, I was lifting all the pieces so many times, that I started to notice another great benefit, the weight. The stock system is small diameter 2.3" tubing, and full of heat shields, and a muffler with lots of chambers and sheet metal. Our system is 3" tubing with no shields, and a much simpler muffler. Anyway, our PERRIN Exhaust system saved 20lbs over stock and, our prototype system doesn't even have the lighter 18ga tubing (it has 16ga which is thicker). OEM Downpipe weighs 5.15lbs where the PERRIN prototype is 4.5lbs OEM Catpipe weighs 14.7lbs where the PERRIN prototype is 7.65lbs OEM Catback weights 43.5lbs where the PERRIN prototype is 31.6lbs So all these pics show the parts, we know it will make more power just bolting it on. But how much is the question. You will just have to wait and see! Within the next week we will provide results doing back to back dyno runs and further tuning with the UNICHIP. HEre are some pics of the 02 housings