In real life testing, admittedly not by me, but comparing evo to 2006 sti, the following was recorded:
Red arrows represent lift/downforce at air flow of 144km/h
Blue arrows represent lift/downforce at air flow of 200km/h
This shows the downforce on the car at speed compared to an evo. It demonstrates that the car is engineered to go light at the front with speed and thus create more understeer as this is acknowledged as being the safest for normal use. It also shows that the rear spoiler/roof spoiler/improved under floor panelling and diffuser on the 2006 STi are actually functional items.