Clicking Noise under load that increases with engine RPM

Hi there,

About a year ago I had my exhaust replaced. Immediately after I picked the car up, I noticed that the car was making a clicking noise when I drove.

The clicking noise only happens when the engine is under load. So accelerating, or going uphill, etc. It does not make the noise (or the noise is not hearable) when you're, for example, travelling downhill without accelerating, rolling to a stop, or sitting stationary.

Additionally, the frequency of the clicking increases with engine RPM.

I initially ignored it for a while as I was told that newly fitted exhausts sometimes sound tinny/rattly for a while until enough soot/dust gets acculumulated to dampen out the noise. However, one year and several thousand miles later, the noise is still there and has no sign of having dampened any.

I'm not entirely sure how much of the exhaust was replaced - but I think the main problem was the cat so I can't imagine that it was replaced all the way up to the exhaust manifold. I had heard that it could be that the exhaust manifold gasket has a leak at one of the outlets, hence providing a click each time that piston pushes exhaust gas through the manifold. But, like I said, I don't think the exhaust was replaced all the way up to the manifold, so I can't imagine that the manifold gasket had been removed/replaced during the exhaust fitting. So not sure if that would be the issue (but maybe!).

Anyway, what do you suppose the problem could be and what steps should I take to troubleshoot?

Kindest regards,
Garrie