mugen twinloop are nice quiet exhausts but are very restrictive so if your looking for performance gains its not what you want, HKS Silent Hi-Power is what I would recommend but hard to find these seconds hand.
you got any pictures cudgs? its a OEM system thats on my ek9 atm but someone crashed into me and the garage screwed me over and ive been left with a bent system thats knocking and ive had a hard time getting a replacement oem so i figured id see what i can get aftermarket wise thats pritty quiet