If the HKS TI for the STi is like the TI on any other car I have heard it on, it is very loud. Loud is not always good. There was a WRX the other day along side me in traffic, not sure what he had but his exhaust was loud and sounded like arse. That combined with the BOV made it sound real bad. It probably sounded good to him inside the car but on the outside it was terrible.
Det./Ping discussed with Service Manager and Service Rep.
I love my carbon ti for my wrx. I've heard louder much more annoying exhaust. It grumbles really low. I think it's the best sound i"ve heard of all the exhausts. Remeber that because we have flat four's it sounds different. Doesn't sound like C/Ti from any other car. It also doesn't really sound too loud because since it sounds so deep, it disguises it. Ive had other WRX owners tell me they prefered the sound of mine, and they had greddy and other big names (one guy was even sponsered by tanabe i think). if you get it you will love it.