A 9k or 10k reving S55 could be a monster.
Interestingly even though the n54 can hit 8200 basically stock DME, as said above, no one ever seems to rev them out, even the vendors. An extra 1k of rpm is significant to say the least.
lol. check the peak power rpm on all of Motiv's dynos for example
I agree, at some point you need more(larger and laggier) turbo. To fight the lag you use NOS to spool it up earlier and more revs so you can take advantage of a larger turbo and not have a powerband of only 6k-7.2k.
lag lag lag lag BOOST!
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Even if power stays constant after 7k I would still prefer to rev out to 8.2k or roughly 15% more revrange/powerband. The wider the powerband and more revs you have the better. You will also be higher in the RPMs after you shift so in a meatier part of the rev range. It could potentially save you from having to have one more shift in the 1/4 for instance.
Again, it seems weird no one revs them out, not even the vendors with built heads. Or if they do they keep the results hidden.