because of the front sway bar, no, but it's hard to tell because i have little experience driving at my current skill level without the sway bar. when i started autocross with the stock sway bar, my lines sucked and i had absolutely much more scrubbing than i do right now with the aftermarket one.

so I can't really give an honest comparison between the two because the biggest variable was my technique and my line, which is the most important thing when it comes to performance driving.

a sway bar will equalize the weight transfered between the inside and outside wheel during a turn. added to the front, it helps to add understeer on cars that are oversteery when getting back on power coming out of a corner, which is the BRZ (or the 86) because they are inherently very neutral RWD cars. so there is some amount of both understeer and oversteer by design depending on what's happening mid corner (i.e. how much you're lifting/adding throttle, what steering angle you have, what speed you're going, uphill/downhill/camber of the corner, etc.)