Mine does it when it is cold as well, so I don't think it is fuel deterioration nor spark plugs. It "should" throw a code if that was the case. It only does it in 4th, 5th, & 6th gears, not in the lower gears. It does it from 2200 rpm & above & only under load does it do it. They extended my warranty but claimed that it was "NORMAL". The Ultimate Driving Machine, should operate a lot better tan that.

Jack