In Season 2 Episode 9 "Good Soldier", go to the end of the episode where Michael is being chased by Carla on the motorcycles. Just before Michael slides under the truck the camera angle changes to where it looks over his shoulder. At that point you can see that the person on the motorcycle is definitely not Jeffrey Donovan (Michael Westen). The rider's hair comes out of the back of the helmet, but Jeffrey Donovan's hair is too short to do that. Also, as he slides under the truck the stunt rider is wearing a glove on his left hand, but when Michael stands back up there is no glove.