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, ESS VT2-650, UUC/Corsa, MS X-pipe, H&R sports, Volk TE37SL 18x9.5+22f and 18x11+34r, Spec TwinDisc P-trim, UCP
'09 Z4 sDrive35i, Deep Sea Blue Metallic, DCT, Premium Pkg, Ivory Leather pkg