1997 Ford Mustang no power

I have 1997 mustang gt with a 4.6 that only has about 30% of its normal power. When I try to give it more than half throttle it just howls real loud and pre ignition knocks as if the timing is not advancing. I replaced the fuel filter and checked the fuel presser. All that is ok. I know its something stupid but I just cant seem to find it. What do you think?