i cant say from experience just yet, but if u find a cheap set of extractors like i did, i'd give it a go, get some experience under ur belt of what they do
its not like u will lose power
i do believe the setup hens sells for the 4g93 is not a direct bolt onto the stock cat, so u will either need to weld them onto ur front pipe or get a exhaust shop to weld it
so that extra cost is something to consider
i hear rumours that stainless steel ones sound tinny, so if u want to be on the safe side get some mild steel ones or whatever the norm is
as usual, 4-2-1 is for a bit of extra mid range and high end power, and 4-1 is for high end
but these setups also depend on how long the actual runners are for each outlet i believe
i have never heard a bad word about hens products, so i'd say his are going to be a good buy for you