Just wanted to let everyone know that after being clever and switching the front brake set-up on my '81 240GLT wagon to power discs with semi-metalic pads I have concluded this is DANGEROUS. I wanted to minimize brake dust and thought these pads would give better "bite." I did not get full race pads as I heard there was an issue with having to warm them up for full grab and being bad for street use. Anyway, after approximately six months of use I noticed a spongy quality to brakes. Then in heavy stop-and-go traffic I would suddenly have REALLY BAD BRAKES with the pedal dropping very close to floor unexpectedly.
I had a mechanic replace master cylinder and it still happened. I changed front pads back to VOLVO factory issue and all symptoms have dissappeared with brakes feeling normal. My theory is metalic pads create higher operating teperatures at calipers and in heavy usage situations this can boil brake fluid at wheels and result in dangerously poor braking when you really need it...Like when the Mack truck stops in front of you in freeway traffic.

BE SAFE (you probably already all are)& merry X-MAS!