will boxster calipers fit b5 2.8q?
 

If so which ones? Will have to change rotors also I assume..

yes

Yes. I'm in the process of piecing together a Boxster brake upgrade myself
 

You've got two options: Buy the upgrade as a complete kit from a tuner (<a href="http://www.purems.com/products/product.php/II=1432">http://www.purems.com/products/product.php/II=1432</a> for example), or piece it together yourself.

You'll probably need wheel spacers to clear the stock 16" wheels (I know the 16" stock sport wheels need them).

If you piece it together yourself, you need:

1) 986 (Boxster) front brake calipers
2) Caliper brackets
3) A8 rotors
4) Brake lines
5) Porsche brake pads
6) Brake fluid

PureMS sells the kit, or you can get just the caliper adapters, brake lines, etc. by themselves if you're piecing it together.

Piecing it together is probably cheaper (used calipers), but the kits are easier and backed by the tuners.

You will need a spacer on the '00-'01 sport wheels. 3mm is about right.
 

I am just setting up everything right now for myself. I havea test wheel, rotor and caliper setup checking to see what I can get away with. Right now I have 2mm washers as spacers, but I haven't bolted everything together to confirm how much space is left between the caliper and wheels.