I have Kappa inlet for more than 10 year on my 16V NA, which is heavily modified...
when I first fit it to the car, I felt some lack of performace down the rpm range, however, engine was stronger above 5000 and could run freely up to 8000rpm, with stock (but ported original 16V it doesn´t run so well in high rpm, but midrange was stronger..)
I have to mention that this behavior was with chip with modified fuel and slightly raised advance (by aroun 1-2°) in whole map..
Last year I tested FC performance chip and it performed wery good with this intake(wery strong midrange, but began lean over 5000rpm..), however, My engine dosn´t have much vacuum (only -0,1bar at idle..), so it had to be live-map (not yet done completely, due to some problems with ignition..) with modified rpm and vacuum breakpoints...
with complete remap, the kappa intake is the way to go...even in NA (look at Thema VIS, which has same intake and 112kW - 10kW moreand revs higher, than coupe 16V engine, with same compression, valves, cams...)