well, anyone that ones jdm headlights know how poop the beam is coming from the H4H bulbs, the only way to increase the output is either spend £70+ on PIAA bulbs, get H4H hids (which only come in single beam), or swap to UK headlights... Or, retrofit OEM projectors into the existing jdm headlight which is what htis walkthrough will show you.
First off, you'll need to get some projectors, there are some good sites out there, namely this one -
http://www.theretrofitsource.com/ loads of good info, you can also buy the projectors on here, but it also shows you what projectors are out there and with some intelligent google searching you ca nfind out what cars they come in as oem.
Theres basically 3 types of projectors - halogen projectors, xenon projectors and bi-xenon projectors
If you wnat to use HIDS, then dont get halogen projectors (ie the cheap ebay angel eyes etc) the beam pattern will still be bad if using hids plus the new mot laws now say they are illegal.
Xenon projectors are single beam, and bi-xenon projectors are hi and low. For this project Im using xenon projectors as im also going to be fitting in the UK main beam headlights in the centre aux position.
So, what do you need? Well, lots of looking on ebay to find cars breaking that have oem xenon headlights, as always I got lucky and I have in my hands a set of Vauxhall Omega xenons (which are hella) complete with the ballast and bulbs for £25, although dont generally expect to pay this little
If they dont come with ballast and bulbs then any hid kit off ebay will work - you'll need to make sure of the bulb size, most oem hids use D2S bulbs.
My lights got delivered yesterday so straight into a hot oven for 4 minutes to soften the glue/sealant thats used on headlights to pull the front lense off, take off anythingthat might melt or get very hot first, so all bulbs, bits of wiring etc then pull the lense off. you can then unscrew the projector housing from the headlight.