Mods, can we make this a sticky??!!
With the amount of threads in here about the same subject and knowing what CVH's are like, can't there be a computer generated reply to such threads??!!
If the car lacks top-end power and/or rattles too, then it has run one or more cam-lobes off, which a CVH engine will do in the blink of an eye.
This is more common if you are running a Piper or Kent camshaft.
Job done.