I have a 2011, manual, FWD.
In hot weather (80+), acceleration lags quite a bit from stop. It can be dangerous pulling into or across traffic, because the car is very sluggish. I rev it up to an unusual degree, but even then the rpm drops dramatically as the clutch engages fully. Sitting at idle, the tach is erratic, and will dip down to about 500, at which point the car shakes slightly as if it is going to stall, then rebounds.
Oddly, the engine temp gauge stays very steady in the middle of its range; there are no indications of engine overheating. The hotter it gets outside, the worse it gets. The problem is very consistent in hot weather. It has continued with regular and synthetic oils. When the outside temperature drops, acceleration and idle return to normal.
I took it to the dealer (difficult logistically) and it turned out to be a relatively cool day, so the problem did not occur (of course).
Anyone else seeing this? Any ideas?