I was just wondering if there is any performance upgrades for an e34 520? I have thaught about an engine conversion and im still considering it but if i can get more performance out of the 520 ill be happy for now. At the moment i have an itg foam airfilter inside the standard air box but tbh id rather a proper induction kit. Anyone know who makes one for the 520? Also is there any performance manifolds/exhaust systems?