How much boost are you running? if you are running factory it sounds about right, it's got nothing to do with how old the car is lol, if you buy a"brand new 99 R34 GTT" striaght out of the showroom now, would be still the same. When you say your exhaust should be all the way from the turbo, did you physically check? or do you just assume. my car ran 155rwk when i bought it 4 years ago, it had a full turbo back exhaust, boost gauge and gay earth cable lol, then after i fitted front mount+pfc, it made just over 200rwk. So yeah good luck with everything and Welcome to the forum
Also you might wanna do a search in "Forced Induction" Section.