So I'm having a similar issue on my brand new MXP. Pulls to the left only during hard acceleration otherwise it's perfectly straight with no pull at static speed. I suspected asymmetrical castor and factory-adjusted toe to compensate for the non straight thrust angle. The problem toe compensation of asymmetrical caster is that under acceleration, the car will start to follow the thrust angle of the caster rather than the toe.
So they checked the alignment and low and behold, the caster was uneven. They did the alignment and it's perfect now.
But guess what? No difference. MXP still pulls to the left during hard acceleration. MXP is brand new with less than 1000 miles, so it can't be a worn bushing.