The best tuning upgrade is to get a Power Vision 3 from Fuel Moto. The PV3 is made by Dynojet but when Fuel Moto sells it you get more tune updates than from Dynojet. The earlier model was called the PVCX, and is a different gadget from the PC5, also used for tuning. It's not cheap, probably $400 or so these days, maybe more. It plugs to your diagnostic port and flashes the computer with whatever tune you desire. You can also use it to log performance, throw those log files into the software and adjust the tune, and flash the bike again.Successive logs like this bring the tune closer and closer to the most effective for you bike. There is a forum member named CraigB1960 on this forum, and on the international forum, who is the expert in getting the most out of the Indians with the PV3.
From Woodrising (no, nobody else has heard of it either) Rides a Springfield Dark Horse