wow... people really missing the point here. Back up and start with the basics

Air Mass = (Engine Displacement) * (Air Density) * (RPM/2)

IE, in a 2.0L Evo X at 4500 RPM using standard temperature and presure:

2.0L = 122 in^3

Air Mass = (122 in^3) * (0.00004671 lb(m)/in^3) * (4000 rpm) / 2

Air Mass = 11.39724 lb/min of air flow

Stop thinking of this in terms of air through an engine, and instead think of it as water through a pump. We're pumping 11.39 lb of water per min, and it's creating a stream.

Now imagine we put a water mill in that stream. How big of a mill? That's up to you. A bigger mill can power a bigger machine. The bigger the mill, the heaver it will be and the more water we'll need to run over it to get it to spin. With only 11.39lb/min of water to work with, if we put too big of a mill, it'll act like a dam and wont do us any good. If we end up needing a mill that requires more water flow than our pump is giving us, then we have a couple options. We can either run it at a higher speed (increase the RPM), or increase the volume of water it moves in each cycle (increase the displacement).

A turbo works the same way. Our engine is equal to the pump, the air pushed through the engine is equal to the water, and the turbo is equal to the mill. The difference is that the pump usually runs at the same speed, while our engine revs over a wide range of RPMs.

We have the same problem. A turbo that exceeds the air mass being pushed by the engine will act like a dam at low RPMs. To overcome that, you either have to wait until you're at a higher RPM, or increase the amount of air pumped per cycle by increasing the displacement of the engine.

Lets go back to the formula. The stock turbo is fully spooled by 2900 RPM. At 2900 RPM, we're pushing 8.27lb/min. That means that we need 8.27lb/min to spool this turbo.

An FP Black seems to hit full spool on a 2.0L at about 4400RPM. Going back to our forumla, this tells us that the Black requires 12.54lb/min to spool. So we're giving up 1500 RPM in spool-time to gain the higher output of the FP Black. This sucks.

We have a few ways to gain this back: Up the rev limit by 1500 RPM (duh), or increase the displacement so that we can hit 12.54lb/min at 4400RPM. Asking for another 1500RPM will take a lot of work and money and prayer... and you'll still be asking for trouble. So how much displacement would we need?

Engine Displacement = Air Mass / ( (Air Density) * (RPM/2) )

= 12.54lb/min / ( (0.00004671 lb(m)/in^3) * (2900 rpm) / 2 )

= 185.10 cubic inches

= 3.03L will spool a FP Black like the stock turbo

Welp... it's not possible to bore/stroke a 2.0L engine to get 3.0L. Just not enough space. How about splitting the difference? Boring and (especially) stroking the engine add rotational mass which is more dangerous at higher RPMs, so the builder will have to use top shelf stuff. We know we can get 2.5L pretty easily. Lets calculate the RPM at which we'd spool with 2.5L of displacement:

RPM = (2 * Air Mass) / ( (Engine Displacement) * (Air Density) )

= (2 * 12.54lb/min ) / (153 in^3 * 0.00004671 lb(m)/in^3)

= 3509 RPM for full spool

Now we're only giving up less than 600 RPM of spool

Raising the rev limiter 500 RPM isn't toooo horribly risky, so you can gain that back.

Well, thats an FP Black. How about a hta86? I cant find a lot of info on them, but AMS did post some dynos. No boost plots, but torque curves usually give a good indication of spool. Based on this, I'd say it spools around 5750RPM

So, how much air does it need to spool? Back to Air Mass = (Engine Displacement) * (Air Density) * (RPM/2). We need 16.38 lb/min.

So at 2.5L, at what RPM should we hit that?

RPM = (2 * Air Mass) / ( (Engine Displacement) * (Air Density) )

= 3790 RPM is about when an hta86 will spool on a 2.5L engine. So a 2.5L with a hta86 will lose a little under 900 RPMs. If you up the rev limit 500 RPM, then you're only losing a little under 400 RPM. Not bad.

Anyway, the bottom line is that putting a big turbo on a larger displacement engine is sorta the reason for going large displacement =/ Raising the rev limit can achieve the same thing, but it's a lot harder to pull off. Just look at formula 1 cars. They rev to 18,000 RPM and make 700-800 hp with a 2.4L v8 without any forced induction. How do they get that much power without boost from 2.4L? have you not been reading? By running it at 18,000 RPM! Do the math and see how much air they're flowing