Well, I'll start off by saying it is
definitely a Mitsubishi, it loves abuse and will take it without skipping a beat.
Redline. Shift. Redline. Shift. Redline. Brake. Shiftdown. Turn. Settle. Throttle. Redline. Shift.
As others have said, it packs a surprising punch for what otherwise looks to be a mundane people-mover. But then again, its got 'dat 1,000+ft-lb of torque' 
.
But seriously, I spend most of my time driving modified & tuned versions of cars in GT, and rarely bother to thrash a stock-stock car around a track with my free-time. Having gone from Sport tires to the CS tires on the Cyborg, I was rather impressed how well it held its track, even at-speed. And the weight-transfer ?, heck that was like a roller-coaster ride, my tuned cars usually corner much flater, so that was an interesting re-experience. My definition of 'Sleeper' is that of the street-racing variety, something that looks stock but performs well beyond expectations. While this Mitsu' does punch above its weight, I find myself conflicted to call it a 'Sleeper' since its not been modified at all, A stock "High performer" maybe, 'top-of-the-line' they say - but its not like its actually packing that 1,000+ tq rating.
This is more of a 'Sleeper' in my eye.