That is really quite expensive. Not really worth it to go such lengths on a 4G15... If 4G9 series, maybe it is okay....Some high performance cars already have them....
Here one by Everco
http://www.zerotohundred.com/2016/v...lled-valve-in-our-clio-4-rs-by-everco-tested/
Example....
http://www.dynomax.com/mufflers/dynomax-vt-mufflers