My 06' GTO LS2 has no power and smells like antifreeze in the exhaust. The check engine light is blinking, exhaust only comes out of one pipe, the motor is misfiring, and the car will not go above 60 mph. I have had several garages diagnose the car and some of the suggestions include bad spark plugs, blown head, or bad head gasket. Does anyone have any other possible suggestions? Thanks in advance for your advice.

Well you can keep driving it until you hydrolock the engine and throw a rod or worse then you will have no choice but to buy an entire engine rather that fix this one.

Incidentally... short of the highly unlikely cracked block or head (these are strong long lasting engines usually).. there really isn't anything else that would do this. I think they ALL have it right.

They got it right. Regularly changing the coolant, with a 50/50 mixture of the recommended antifreeze and distilled water, and properly refilling the system to prevent entrapped air, will virtually eliminate these problems.