you can also use the #74 size LEDs in place of the bulb. i used a blue LED and it's significantly brighter than than what it used to be. i also used the #74 LEDs inside the gauge cluster, but the light dispersion in the gauge cluster isn't as good as in the boost gauge (ie boost gauge is brighter than gauge clusters)
i got my LEDs from here: http://autolumination.com/74.htm
you can also find them here http://www.superbrightleds.com/specs/74_t15.htm
obviously, these are not the only places you can find them and you can probably find better prices elsewhere.