No probs Phil .
With the STi having 4-pot Brembos on the front you need a wheel with an offset of ET45 for them to clear the callipers (But only just though).
I thought the Tarmac wheels I bought had an offset of 45, but turns out they're only ET48. I fitted a pair of 3mm spacers (About £10), which gives the brakes 1-2mm of clearance, and brings the offset back to the desired 45.
I think the bigger the offset, the less clearance you have? I did have a good diagram explaining exactly what all the wheel dimension actually translate to. I'll see if I can dig it out.
Cheers,
Phil