Noticed something interesting today

[adrian k]

two weeks ago i fitted a set of 18" TE Azzuro wheels on my AU3 XR8, and i have noticed something different about the way it drives. With the factory 17s, when gunning it, it pulled nice and straight, but now with the 18s, when giving it the herbs and it changes down, it seems to pull to the left, but steering from the rear, then when still under load, you take your foot out of it, it pulls back again as the engine starts backing off. its actually quite noticable, on both ON and coming OFF the power, even the wife noticed it today. interestinly enough, the steering feels lighter in the front end than it did with the 17s at low speed driving.
has anyone come across this before?? could it just need a wheel alignment with the new 18s?