I know that you can put the TT brake caliper carriers on an a4 to run a8 rotors, is it possible to just bolt the entire a8 caliper to the a4? If so is the a8 caliper better than the a4's?

email me for details.

Kinda like this? ;-)

<img src="http://expert.ics.purdue.edu/~fergusoe/Misc/DSCF0001_SM.jpg">

Not much to it, just gotta get proper caliper carriers.

Don't think the A8 caliper would be other than heavier than the OEM...?<ul><li><a href="http://www.audiworld.com/tech/wheel1.shtml">A8 Brakes for other Audi Applications</a></li></ul>

Which year/model did the calipers come from?

That was my roommates car, RIP (it was killed by a Z71 in November). Rotors are from an A8, forget which one (312mm?). Calipers are from a Boxster (standard model).

<img src="http://pictureposter.audiworld.com/27056/dsc03875.jpg">