General PIAA foglight question

[Yaristeve]

I have been thinking of installing foglights on my 2011, 3-door. I find that a good foglight (not the crappy, mostly cosmetic factory stuff) is great for lighting up the highway lane lines in very heavy rainstorms. Rather than buying a pair of tiny PIAAs to install in the factory location, the thread on "rally style",

http://www.yarisworld.com/forums/showthread.php?t=40198,

got me thinking how I like the look of those huge fogs on the front of rally cars. So, I decided buy a pair of 5", 6", or 7" lamps to mount above my bumper. I am undecided whether to get NOS Cibie Oscars or PIAA 520 or 540 series lights. My question is about the PIAA lamp covers. They are a grille style "cover", not a solid cover like the Cibie Oscars'. They also have PIAA cast in them. My question is, are the PIAA covers supposed to be removed when the lights are turned on or are the covers left on when the lights are on? I searched many hours on the internet but I can't find any answer.


TIA...