That model is where you're problem lies. The organization of polies defining the bonnet and windscreen are particularly horrid.
Re-model it using some nice symetrical quads, along the lines of the pic below (doesn't necessarily have to be this hi-poly), and it should texture fine.
Re-model it using some nice symetrical quads, along the lines of the pic below (doesn't necessarily have to be this hi-poly), and it should texture fine.