I bought a used prius and would like to have a HID headlight (with ballast installed), but the point is that my yellowish headlight is brighter than others so I suspect that there were a ballast for HID inside, but not the lamps itself - then to upgrade, I should buy just the HID light (not ballast cos ballast cost hundreds for 2 as well) Any suggestion is highly recommended on how to check and how to install on Prius 2005, no NAV? What if I just replace my yellowish lamps with HID without ballast, will it compatible/work?