The TDI ratios are all wrong. The 5-speed box in the mk4 gti is fine - with stock internals, and a safe rev limit, running on 195-50-15s my mate went through the trap at Bruntingthorpe at 155 and the car was still pulling.
Just to amuse, I'm pretty sure a 02m 6-speed gearbox is around 50kg!
The 02j derived 6-speed I mentioned, is known as a 02S. Deffo worth a look, as it's more likely to fit than the 02m, and weigh less.
