i know a mondeo st with scaffolding pipe used as a straight through lol, its loud but it dont think its as loud as a buddy club spec 2 for a type r or maybe coul be the same
http://www.mkiv.com/techarticles/filters_test/2/ have a deak at this, they test the hks, apexi, blitz and k&n induction kits on filtration and gains. be surpised of the results
a lighter flywheel will reduce rotational mass but you are supposed to lose momentum going up hills compared to a standard but makes heel and toe even better. also the car will rev more freely
miester r's are made for uk roads so ride quality will be good and im sure they can be adjusted, dont know about how low you can go but personally i would go for them