Strange Knocking under Acceleration

Now my problem is this. When I accelerate the car there is a knocking sound that appears to be occurring somewhere around the rear left of the car. The knocking gets faster as the wheels picks up speed and seems to be cyclic in nature. I thought this might be a RTAB, so whipped of the wheel and had a look and to my surprise found a small piece of RTAB. Thinking I had found the culprit I ordered up my Powerflex replacements. On removal of the LH one I almost convinced myself this was the defect due to the state of it. The out case had almost corroded to nothing in parts so even if it didn't clear the knocking noise it has fixed something that was particularly broken.

The suspension has been changed to koni adjustables. The big bush on the diff has also been changed to a Meyle HD. Below are the pics of the RTAB bushes I pulled and subsequently replaced.

Now I know my RTAB's are good, Shocks and springs are good and big diff bush is good.

What else can it be?