actually he is not...kind of right in a way...thats why you may have noticed lots of s/c on modern cars..(mercs,bmw's etc)
modern supercharger setups dont always run the supercharger on load..ie on tick over,crusing,over run they are not on load and draw no power(well bugger all)..this is due to the boost being vented into the intake thus unloading the s/c and hense very little power required to spin it...
when on load though power is sapped as my 112 eaton draws upto 50hp to give max boost..the control for this is mechanical and vacum from engine controlled (vac opens valve,valve unloads s/c)
however..turbo's use "free energy"..ie exhaust.but even that is not free,for example as just bolting on a turbo without proper research,as too big turbo =massive lag..too small=restricted exhaust,no top end power..most turbo setups ,even moderm oem setups are a compromise..
so yes a supercharger will work on your engine..but you got a turbo ..so why ever considering s/c??
also..a supercharger is good in economy issue over a turbo at low boost as its instant..and hense you have more bottom end torque..if used wisley can give improved mpg,espically over a n/a engine(really applies to petrol lumps more as dieasels tend nt to suffer from lack of low end torque..)