i too love my yellow piaa 510 fogs. i have philips bluevision bulbs that i swapped in over the sylvania ss.
ss
lumen (low hi 1000 1350) color temp 4000k
philips (low hi 1132 1738) color temp 3600k
i wanted whiter light output with hi lumens. the ss were too close to the hid color of 4200k and ultrawhite is 3800k so the 3600k color works great for me along with better lumens. the problem with nonhid higher color bulbs like the philips and especially the ss (higher color) is they are worse in rain and snow. thats where the yellow piaa fogs really shine.
but these hir's are something to strongly consider if the lumens is legit. and the color is 3600k, same as my philips.
$120 for 4 new 9005 pir's is too much right now but will go onto the to-do list
