your best bet is to just get a wiring harness with a relay. power to the ballast should come directly from the battery, and not through the stock wiring. the setup would then be:

battery -> 20amp fuse -> relay -> ballast -> bulb (repeat 2x)

and the stock 9006 harness would then act as a trigger, connecting to the relay to either 1) turn on, or 2) turn off the HID. the ballast will automatically regulate how much electricity it needs. your stock wiring might be offering too much resistence right now, not allowing the ballast to get enough electricity to start up and maintain the system. think of your stock wiring like a 56k modem and the HID ballast needs broadband streaming in order to boot up. not sure if that analogy helps you visualize the current problem. a metal wire conducts electricity. but it's also a resister. if you don't give it enough juice, electricity can't flow through it. if you give it more juice than the wire can handle, then it heats up and can melt.

but if you're not sure what i'm talking about, take it to someone who installs car stereos. the ballast is like an amp. all the installer needs to do is insert a relay between the ballast and battery, where the relay is connected to your stock 9006 harness.

or you can sell off your old PML kit and buy a new 9006 kit. just about all kit (even the crappy ones) come with relays nowadays.