I have an issue with powersteering on a 97 VT V6. At idle the steering is very heavy (lack of powersteering) which makes parking it a real pain in the arse. It doesn't happen all the time but is getting more frequent. Give a bit of throttle and it is ok. Can't spot any leaks any where and haven't lost any fluid level, I have disconnected the rack to check that the wheel assembly turns freely which it does. So I have narrowed it down to either the pump or the rack.
Any suggestion would be great