Before dismantling the rack itself check the clamps that mount it to the tub.
I had this on mine, the u bolt at the drivers side had come a little loose and the rack was moving slightly when turning the wheel. This would be my bet.
Unfortunately the nuts on this bolt are on the inside of the tub, so it's a head down inside the footwell job, hope you're not claustrophobic...
The access hole behind the pedals will probably have been covered by the builder.
I'd actually recommend anyone check this mount if the cars done some miles since built, and if you do have to get down inside the tub you can always check all the suspension nuts that are in there while you're there...
Cheers,
Mike