I've got a JB4 G4 piggyback without the harness for sale. I never had any problems with it and it's in perfect shape.
Upgrade your AA AP2 or JB3 for cheap!
'09 E93 M3 6MT, H&R sports, VMR710 19x9.5+22f 19x11+25r, Michelin PSS, VF540, AA TPs
'09 Z4 sDrive35i, Deep Sea Blue Metallic, DCT, Premium Pkg, Ivory Leather pkg