The first is the HGTE pack. – the H standing for "handling", GT for "gran turismo" and E for "evoluzione". So the HGTE pack will give a lot for the 599 to make it feel "refreshed" from its debut in 2007.
The new pack gives 20-inch light-weight modular wheels wrapped in fresh rubber, a "thrilling" retuned chrome exhaust, new front mesh grille, upgraded and stiffer spring rates, revised anti-roll bars, lower ride-height for lower center of gravity to improve handling, improved electronics with faster F1 gear shifters, and a new engine software strategy has improved accelerator response.
Inside, the Handling GT Evoluzione package gives the 599 a much more hard-core sportier look. With full gain of leather, black Alcantara and naked carbon-fiber trim. Seats are finished with Alcantara leather and seat backs are trimmed entirely in carbon-fibre. Embroidered in contrasting stitching on the headrest, are a Prancing Horse and the words “Handling GTE".
The second model of the 599 GTB, is the 599XX. It's a showcase to the Ferrari FXX F1 racing development program. So the 599XX is a road-legal car that is packed with Ferrari's F1 technology. Only 20 or 30 units will be built, and Ferrari will offer them to "special" costumers.
While it's based on the 599, the Ferrari F1 racing team have done some extensive treatment on the body, giving it a deeper front-splitter, side skirts, aero dynamic mirrors, Michelin F1 tyres, and a fixed carbon-fiber rear-spoiler with a twin rear-diffuser that give 280 kg of downforce at 200 km/h. Ferrari also messed with the engine compartment to make the 6.0L V12 sing all the way to 9,000 rpm and give 700 hp! So already the Lamborghini Murciélago LP 670-4 SuperVeloce has a strong rival.
Source : [Ferrari]