It does like to wander a bit on the freeway over bumps and grooves. Right now it's bone stock, though I switch back and forth from the OEM steelies to Civic VX wheels with good tires from time to time.
At the second dealership, they're Diamond rated for customer service, and they had checked mine out side-by-side with a brand new one they just got off a truck a couple days before, and it was the same as mine. It was explained to me that the wandering is the result of the car's light weight paired with the very skinny tires. That's why I decided to contact Mitsu directly, and we'll see what they have to say about it, since the conflict of whether or not it's in spec is a valid concern.
It did feel a bit better after the toe adjustment, and I got to pace it a bit through some curvy country roads, and it's actually not as bad as I thought it would be. My guess is that the negative camber in the rear is designed in to help compensate for the narrower rear track width. Either way, I plan on lowering and stiffening the suspension, and will probably adjust the camber settings to my personal preferences at the same time.
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View my fuel log 2014 Mirage DE 1.2 manual: 49.2 mpg (US) ... 20.9 km/L ... 4.8 L/100 km ... 59.1 mpg (Imp)