So, if your 2.0L engine draws in 1.0L/revolution, then if you're doing 7000rpn you're drawing in 7000Litre/minute and adding say 1.4x gives 9800litre/minute or just about 350cfm.

Surely this is wrong? Seems very little to me. Is the point for big exhausts, IC pipes etc simply to cope with the flow impulses? Like say on average the flow is low but is actually a series of very high flow rate pulses?

I'm not an expert on the combustion process, so please be nice.

 

Running at a theoretical 90% VE at 7000rpm, the volume of air going through your engine would be around 222cfm. It seems small only because you are looking only at the volume of the air. In reality, because the air is being compressed at the turbo, the volume of air running through the intake and exhaust system is much greater.

For example, if you're running 1.5bar of boost and if your IC were 100% efficient (it isn't), you'd see ~550cfm flowing through the intake, or about 2.5 times the compressed volume flowing through the throttle body.

 

Ted answered it well.