its something to look at, atleast if you have the same issue i have found the solution..

Another forum member did also mention that they needed to put a 3mm or 4mm spacer on the bottom bolt(s)???

cant remember who tho.

i did mention it in another thread, maybe it was me...lol

I do believe it was you

Just resurrecting this thread with updated info (for the future). Ray (snap0946) and I just fitted a dual booster and uprated master to my AU 1.5 XR8. No hammering was required to fit the bigger booster, the AU 1.5 (Jan 2000) seems to have has a different firewall than the AU 1 series as it it the same as the AU2's.

The only thing we had to do was to drill 4 holes for the booster, all in different locations than the original 2.

Car stops way better now with BA front calipers & rotors and standard rear brakes.

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Cheers
RD