Brake caliper OEM Volkswagen or OEM Porsche

i have the same thing on mine, with rear disks & MKIV calipers, it stops on a dime

I run TT rotors with Boxster calipers. I like this setup very much. Brake pedal is a little firmer than stock and they are easy to modulate on the street.

Braking is sure, thanks to large four-piston calipers all around, though the pedal effort is not as progressive as I'd like.

I had this problem with my 90 GLI. It was the parking brake mechanism on the caliper of the right rear wheel. It had seized, not allowing the caliper to release when I released the parking brake lever. I had to replace the caliper.