factory redline on a 996 turbo is 6200 rpm. mine is modded so redline is 7000 but the ecu records every cycle over 6200 as a type 2 over rev.
also its apples to oranges. twin turbo vs small s/c 3.2 v6 vs 3.6 flat 6. 2 completely different animals.
on my slk32 i had as high as 6900 rpm rev limiter and it didnt do any good. outside the peak limits of the engine. power is at peak boost from about 2200 rpm to about 5900 rpm. after that your just beating on the engine with little gains for the effort

dont forget the s/c boost is almost 90% at 2200 rpm and turbo boost climbs from 3000 and builds as the car revs higher until peak turbo efficiency at about 6000 rpm. (maybe a bit higher with proper fueling and tuning)