i just bought a 300zx and it has a knock when is warm at 1500 or 2000rpm, i dont now anything about this cars so the only thing that i know is what the car recive his oil change the last month and a cleaning on the inyector. please help me i dont wanna now what it can be the cylinder head or any expensive thing. thanks

 

found these vids my car is doing the same thing havent done it yet to see if thats the cause or not