Put mk3 ones on, from a later model Mk3 tho as the early ones tend to seize too. I had same problem with my rears, one seized and one fine. I fitted mk3 rears to mine, was a long time ago so not 100%, may have been GTi callipers, but either way there still working perfectly. A straight swap, (mines an '87 GTi) the only difference on the mk3 calipers the handbrake cable/brake line is opposite to the mk2. DONT put the callipers on upside down, keep them the correct way up and swap the handbrake cable/brake line around. Piece of cake!!