This may not be relevant, but the cables between the GQ, G2, P2, T2 power suppliers from EVGA are not always interchangeable - the pin wiring is different on some.
I had similar clicking which was down to mixing up GQ and G2 cables.. Took ages to find!
Agreed, avoid switching cables between different modular PSUs, even those from the same manufacturer. They might not work, or worst case, using incompatible cables can cause permanent damage to your system.