^ this or your voltage regulator
Test the "proper" way. Your indy should have load testing equipment in-house. Under load, e.g. with car running, your regulator should push out min. 15.x volts. Not sure of the correct value but it's not 14.4 like many think it is
If not above 15.x volts then your regulator is shot ($50 part of similar?). Change that and your spoiler, multiple LEDs and aftermarket lights should shine like a diamond all over the place again brother
(or could be as simple as a bad batt throwing out less AMP 'than advertised on its sticker')
Luck