Forgive me if my jumping in is unwelcome. The 5-cyl con-rods are the same 144mm centre-to-centre length as the 1.9, and the big-end diameter is the same as well. Donno, about the wrist pin diameter, but I imagine if the pistons and rods from the 2.5 are both swapped into the 1.9 there shouldn't be any problems. However, I don't know if the piston protrusion over the block deck will be the same. The 2.5 150HP TDI has a 19:1 compression ratio and apparently differently shaped bowl.