I have/had a Magnus on my 96 Talon. Yes the autocross car had a sheet metal intake. It definitely flowed top end 5500+ a hell of a lot better than stocker. The difference was more noticeable when I swapped out from some HKS cams. Now did I do any testing with other SMIM? Nope. Did I loose some low end torque and mid range. A bit. Spool up increased 200 -300 rpm but the extra 1500 RPM - 2000 RPM of pull made up for that.
Is it for everyone? Nope. Throw a sheetmetal intake, ANY Sheetmetal intake, on a completely stock DSM and you will wonder how anyone could sell such crap for that amount of money. throw it on a built machine with a well match parts profile and you will wonder why you didn’t do it sooner.
On evo’s it may be a different story.