If it's a Mk.1 Leon, then the only diesel 110 BHP engine is VE (Verteiler i.e. Distributor Pump). The 1.9 TDI 90 and 110 engines are both VE: The PD's are 130 and 150.
There's a lot that can be done with the TDI 110 engine, some reckon it to be the best one to mod. Remap, bigger turbo, bigger injector nozzles and so on. 150 BHp is within reach, and I'm sure I've read of 200, though that would be fairly exotic. Don't forget to budget for better brakes. The standard clutch should be OK up to 150, but that's about the limit.
The TDI 110 comes with a five speed box as standard, and a slightly smaller clutch and flywheel than the 130/150.