Just my two cents, I tried to control as many variables as possiblw when I did before and after dyno runs with the addition of German-made TTP headers to my 2000 2.7L Boxster.
Depending on the run, I only saw a 3-5 hp increase at the wheels, less than I expected, but the headers sure make the exhaust system sing, at least to my ears. The downside is that I have been messing around with check engine light after the headers went on.
Ed
