Do I have a blown head

have your cat converter checked and if it is bad, find the reason it failed. Roy

There are a number of things but the first thing to check is the ignition coils if you do not have any diagnostic tools wait until it's dark and see if there are any sparks emitting from them then replace the ones that are bad. There are many things that it could also be but check the fuel system filters, pressure. Does the car smoke if so what color that will also tell you a lot from the car. Good Luck! On the Q45 they have about the best breathing exhaust you can get so I do not believe Catalytic converter too be bad but it is possible.