The standard pee-shooter twin tail-pipe of the Impreza had been bugging me for ages. I then saw someone advertising an STI 3" back box on Scoobynet for a mere £75. It was brand new having only covered a few delivery miles on the back of a P1.

My first thoughts were to hand the box over to my Dealer to fit, but when someone told me it was only a 10min job I thought I'd give it a go myself. The back box is only held in-place by two bolts (mated to the centre section) and 3 metal hooks that insert into some rubber grommets underneath the car.

From the picture above, you can see the two holes at the rear of the exhaust which connect to the centre section. The first hook just before the back box chamber and the final two just before the tailpipe.

There's an excellent fitting guide here, but here is a couple of pictures to help.

1 - 2 bolts. 2,3 and 4 hanging brackets.

close-up of the centre connection (circled)

I also source an STI de-cat centre section from Scoobynet for £30. Again, this is an easy job with just a further two bolts holding this section onto the Downpipe. The STI version looks identical to the OEM one it replaced, the only difference being the removal of the catalytic converter.

I never noticed any performance gain swapping the back box and de-cat centre, just a nice increase in the deep flat-4 burble.