have you been reving it in netral then dumping it into gear if you have then you are experiancing severe slippage
sometimes if you leave the car off for a while and let it cool down fully it will return to normal
if its not there tap into the ignition wires from behind where you put the key in
you will more than likely have to run a relay as the alarm will either not arm when the cars on or it will go off when it is armed