'Are the ribbed belts and tensioner pulley of a 1.9 TDI engine with the code AFN (Golf 3 with 81 kW) compatible with a 1.9 TDI engine with the code ASV (Golf 4 with 81 kW)? Are the ribbed belts and tensioner pulleys identical for all 81 kW models?'
The AFN has a torsion spring, and the ASV has a hydraulic tensioner (but I'm not entirely sure about that anymore - it might also be a torsion spring, but a different one).