Ok thie relates to my last post ... Tried to copy info and add using the phone ... Didnt work ...
Anyhow, just thought, if there was no change between having vct connecyed or not, could that not indicate that the vct is not working?
Also, excess fuel flow is iften used the keep the fuel rail cool. The fuel rail gettinh hot to tye point if discolouraton my indicated that you hage reduced flow out of the rail and hence cooling flow to the rear injectors or you have something making it hot. This would heat the fuel and change the fuel flow out of them. If up, the ecu would lean out the others if flow goes down, well theres your knock.
Just my thoughts.