Charlie,
PAS systems tend to groan when working under heavy loads and when at standstill this is very hard on the system. We spend hours and ££££'s at aston tuning pipes and to try and eliminate the groans and other noises. Check the condition of the belt, its tension and as long as there is no play in the rack you will be fine. Had to replace mine after the last race of last season after one of the rack shaft bushings gave up the ghost. Did consider dropping the PAS system and going manual but need more time in the gym before giving it a go.
Give me a bell over the weekend and tell me how Cadwell went.
Cheers
Craig