My 172 cup that I got back in July was pulling right under throttle from the moment I drove it home from the garage. If I backed off the throttle, it would drive straight. I read all of the potential remedies on this forum but wasnt sure what to do as the car only has 34k on it and I didnt know where to start with regards to checking for wear and tear plus I had other bits to sort on the car before I got round to sorting this annoying issue out (full service, belts, battery, replace mickey mouse lexus lights etc) . I have checked the old service history and mot reports and it transpired that (only) 1 of the track rod ends had been replaced about 10k a go - this morning I changed both track rod ends and ball joints, had it tracked by kwikfit and now it is all cured - can start loving my cup now as it is driving and handling like my old 172 cup (which i should never have gotten rid of).
Only cost about £45 for the parts from my local gsf motor factors and its the best £45 I have spent on it! Might be worth trying this as its not expensive anddepending on your mileage, they may need changing anyhow