The G5 is the new JB4 basically. It has an upgraded board which supports new features:
Like isolated boost control, build in CPS (timing control), speed limit defeat, NLS/2Step, better fueling control.
Check the link below for more info
SOLD --'07 E90 335i, PTF COBB E50, HFS4, ER CP, ETS 7", AA DP, Vishnu Exhaust, DCI, ACT, Nitto Nt555
SOLD '10 E92 335i M, 6MT COBB v3, ER IC, ER CP, VRSF DP, Fuel-it st2, Mfactory LSD