A couple things to add here to the "thoughts" end of it.
A properly sized and efficient street turbo will be at full boost by about 2200 RPM and carry full boost to 6500 ish if the rest of the system flows well (cam timing, intercooler, piping, manifold). To have to turbo "hit" at 3500-4000 you'll be using a "too large" turbo for the street and it'll be like a turbo bike of the 80s, a turd below 3500 and then a massive hard to control rush up the boost curve, not fun, and not fast because the lack of linearity will stop you from opening it and holding it open. You can force a correctly sized turbo to come on late....but why? Thinking larger K04 without a twin scroll inlet is about the right size, like used on Audi RS twin turbos (the bigger ones).
@Torque addict can elaborate on what a properly sized turbo R3 feels like.
Someone asked what torque on a 240/265 bike is at 3500-4000, well, there's 3 recent third party dynos that show that range now posted on these here forums. Answer 140-170lb-ft depending on the particular build, so giving nothing up mid-range. It's below 2800ish where 20-40lb-ft will be missing from the Carpenter bikes. Mind you, that's still between 110 and 140 lb-ft depending on the build, so, in short it's plenty of torque to pull cleanly away.
Neville's builds I've seen plots for are distinctly different curves from Carpenters and should not be lumped in as "NA built rockets", their power curves are very distinct.
You CAN have your cake and eat it too with 150+ lb-ft from 2,200-7,000 with a peak in the high 170lb-ft range using the right parts from the right suppliers.
Also, a note on 9,000 RPM Carpenter bikes, their power over 8,000 is falling off quickly and there's precious little reason to spin them that high outside drag racing. My 265 kit peaks at 7,800. Intake cam timing could shift the peak up to 8,200 or so and gain 5hp, but it murders torque down low by doing so.
I've yet to see any rocket that peaks over 8,000 NA, and for good reason.
EDIT: I do recall 1 NA build peaking just over 8k, I think Ponters bike did on the original graph he posted.
