Mystery sound

hey my 2.2 cav also makes another wierd sound. Under higher rpms (for instance holding 4th gear at 160km/h or 100mi/h) it makes a really weird knocking sound. It does it when I let off the gas under high rpm. The engine only does it at higher rps. I just replaced the spark plugs and plug wires, coil pack and fuel pump. Any ideas what could be causing the sound?

The rubber in my motor mounts is cracked and worn out. Not sure if this could be part of the problem. Any ideas?

Also when I turn the car off something rattles and the car shakes a bit. Not sure if its just a vacuum leak or something more serious. The cars got 247,000kms on her. Im not afraid to wrench on it, but I can't figure out whats causing these problems. Any ideas.

im wondering why you are running that car at 100mph???

im wondering why you are running that car at 100mph???

why not? the aerodynamics of a cav aren't too good and the steering wheel gets loose. hahahah

I got all new suspension, new brakes, ram air. I do alot of highway driving and sometimes I push the car harder than I should.

But the engine will even knock when I hold 60km/h in second.