i had a Magnex system on my MK5 GTi for about 3 weeks
it was a very nice well made system and good value, i paid £350 for it at the time
it was embarassingly LOUD and i hardly drove the car when it was on
i phoned the shop back that sold and fitted it for me (drivers in Glasgow) next day
Drivers agreed to exchange it for a Miltek because they to were very surprised at how loud it was
i start work at 6am and had to crawl out of my street to avoid waking people up in Edinburgh

don't buy one, it wasn't even a nice sounding loud and it just didn't suit the GTi
on comparison the Miltek (resonated) is only slightly louder than standard