I remember Solutions were claiming 325 cfm for there scorpion a few years back! and 425cfm with the Booster connected to it
 Scorpion was three 450airwatt 100CFM three stages in parallel so not far off the 'claimed'  325  ,     
 If u look at Cleansmarts enforcer vs Airflex turbo on Youtube , they measure 305CFM for the  Airflex turbo using similar motors .
And if you add an inline booster like you say you get 400+ CFM .
But CFM is only one measurement in gauging a vacuum systems
performance  , including the waterlift / HG  measurement gives a
better overall indication of performance .
The four high airwatt motors in the Mytee Escape are connected in
series and parallel  , the second pair of motors are pulling through
the first pair which increases the system lift .
Compare the numbers for the Scorpion / Airflex turbo .
Three 450 airwatt 100cfm motors in parallel give 300+ CFM   .....   Lift will
be 10HG ( 137" waterlift )
Add you inline booster you get 400CFM but system lift remains at 10Hg
Four 600+ Airwatt motors in series/parallel in the Mytee escape  give
325 CFM  ....   but water lift is  16.5 HG ( 230" waterlift )