Small glitch on mission 2 :
After you leave the casino, when you are on the top of the vehicule of Karl Blaine, some enemy vehicules are chasing you.
Instead of using a lot of ammo for destroying them, you can simply jump out of the car. Karl Blaine will stop, the enemies too, and... they ignore you. You can go close to them, and shoot them, ... they don't even look at you (as long as you don't go back on top of the car)
Good luck