Please Help

I have a 97 firebird 3.8. I am getting the code p0300, and when i accelerate the exhaust pops. The cars has no power, and when i try to drive the car it starts to overheat, but when i just let it idle it never gets hot.

I don't know how much help this is, but the code decodes as: Random/Multiple Cylinder Misfire Detected
You can look up codes at: http://www.actron.com/code_lookup.php