Heres a video bud to show the sound outside the car.
http://smg.photobucket.com/user/dan...DDAE0E35-14FC-49F0-A88A-0AF7BC77743C.mp4.html
If the video works, the hissing sound comes through the cabin but isn't too bad if you play music all the time. Also for the cost of the kit circa £25 it's not an expensive mod if you do not like it.
link doesnt fetch anything up i've heard many mixed reviews about it all thats all!
you have to mess about with a boost nipple as ive seen mentioned like this? http://www.ebay.co.uk/itm/321796943388?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT