G-T mod uses a HP system developed for the RR Trent 700 engine.The module has a weight decrease of 200lb per engine, 2 to 3% improvement in SFC and approx 25 degrees C reduction in TGT at T/O thrust.
HPC- Stage 1 root redesign to reduce windage and eliminate leakage path.
Combustor- Low emissions combustor, reduced total volume, double sided dilution system.
HPT- Improved efficiency,tip clearance control.
Also more fuel spray nozzles with new design.Oil return tubes increased diameter,redesigned bearing vents for better flow.
Hope the info helps.