My vote goes to a vacuum leak in the intake system. Think about the problem and the way your car operates - when the car is cold the DME reacts by enriching the air/fuel mixture (which will tend to mask uninvited air which enters the intake system via a vacuum leak). When the car warms up, the DME leans the air/fuel mix, which will result in an excessively lean mix, resulting in poor driveability. Admittedly crank position sensor malfunction can replicate these conditions as a bad one will often work when cold and break down as the engine warms up.