Those yellow 6-piston calipers are from Porsche GT2. I have such a set going under my Porsche 944 Turbo. rear axle have Porsche GT3 rear calipers. Here a picture from which you can see also the adapters for front & rear calipers and also an adapter which brings handbrake shoes outwards a bit, so you can use GT3 rear rotor. These adapters were designed by my friend & I. My friend have a similar set up under his 944 Turbo.

Most likely i am going to use these calipers (996 carrera rear caliper) at front axle, because they just fit with inside original 15" wheel.

There is not necesserily any need for this upgrade, but i just have these calipers laying around, so why not use them

Calipers which are in the first picture i posted are from left to right:
GT2 6-piston, GT3 4-piston, 993 4-piston (same as Audi RS2 had), GT2 6-piston, GT3 4-piston rear, GT3 4-piston. Those black small calipers are 944 Turbo front 4-piston calipers.