Shimmy at high speed going uphill?

[WeaponizedOne]

I'm tuning the MR2 1600 Supercharged and I've encountered a really odd problem going uphill. I've been playing GT since the beginning and never run into it. The car acts as though its going to oversteer, but then understeers a bit, goes back to the beginning and starts again. Never actually lose grip or begin to slide, but its odd.

Anyone run into this?