Thats a strange Problem , It could be a wiring Issue , Perhaps you not getting enough Power to the Left side ?
Is the headlight in your Car a Projector headlamp ? Because a projector Lamp is needed to focus the HiD correctly .
Maybe you could add a relay to the Circuit it the Power is Not Enough
"Why Would you want to use a relay and do u really need to? Anytime you want to switch a device which draws more current than is provided by an output of a switch or component you'll need to use a relay. The coil of an SPDT relay that we most commonly use draws very little current (less than 200 milliamps) and the amount of current that you can pass through a relay's common, normally closed, and normally open contacts will handle up to 30 or 40 amps. This allows you to switch devices such as headlights, parking lights, horns, etc., with low amperage outputs such as those found on keyless entry and alarm systems, and other components. In some cases you may need to switch multiple things at the same time using one output. A single output connected to multiple relays will allow you to open continuity and/or close continuity simultaneously on multiple wires" Quoted from http://www.the12Volt.com
Please View that Site for more information Regarding Relays