I toyed with removing the sports cat to see if it helped, i bought it new but it was supposed to be a 200 cell,but wondered if it was restricting it slightly?
I’d say you’re doing really well for a NA motor at present - to get much more (particularly if you’re into torque) then your plan of supercharging sounds like the only sane way forwards 
My KAAZ close ratio box makes mine feel punchier in all gears - it’s obviously bound to have that effect - but you need to change gears more often…
An internet-friend has recently supercharged an NA car, not with an MP62 but using a TVS1320 from SSC in Aus.
what kind of extra import costs did he incur? i need to find out the bottom line/total costs to convert