i was told that an HKS HI-Power exhaust for an STi was made for an sti with an aftermarket downpipe,but the hks site says nothing about it..anyone know the truth?
Whats the difference? If you're using a US spec'd DP there shouldnt be an issue between stock and aftermarket. They're the same length unless you're buying a shorty DP. Perhaps that's what it is implying, however, Ive never heard of this. Im fairly certain Brian uses one, be sure to send him a PM!
Sti and WRX catbacks are the same. Same with the downpipes. You don't want to go with the HKS downpipe though. Its not the best design, since it still uses a flat plate like stock behind the wastegate. This will decrease the flow of the wastegate. Go with a bellmouth or divorced wastegate pipe design (Maddad, Perrin, Invidia, B&B, etc...). The downpipe does not come with the catback.