| I guy I know in Italy owns a highly tuned 998S and a Termi 54mm full system as well as a Leo Vince 57mm full Ti system.
He uses his bike for both street and track and he says the 57mm system is only marginally better above 9.500 rpm. Apart from that narrow, but crucial, rpm segment the 54mm system is significantly better all across the midrange etc.
Don't fool yourself, though. If you're not into full-on racing you're not spending much time at the rev limiter end of the rpm band and therefore you should focus on allround power delivery instead of peak performance at the top end.
I think you need to ask yourself what you're really after. If it's the bling factor and you don't mind losing engine performance all across the board using a stock 998S engine then go ahead and buy the biggest, meanest system there is.
On the other hand, if you're actually planning on using your bike on the street when you're not attending the occasional track day and you want to maintain the allround performance qualities of your engine the way it is today I'd either stick with the system you already have or tune the engine a bit and aim for the 54mm system.
A large system like the 60mm or 63mm is only going to be useful, performance wise, if you are planning on tuning your engine to the level of a 996RS/998RS.
Yes, these systems allow the engine to breath freely but if your engine isn't capable of delivering the amount of gas flow these systems were designed for you'll lose engine performance instead of gaining power.  | 
16-Dec-2006, 11:56 
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