I have the ESS Profile NVG's and removed the foam but they still fog like a bitch. So bad in fact, I now pretty much only use my JT goggles which have NEVER fogged on me.
I'd suggest having some sort of anti-fog spray handy. A lot of people swear by Fog-Tech and this other one called "Cat-Crap" or something.
Guardians of Asgaard - KF25 -
Primaries: LCT AS VAL, LCT AKS74UN, VFC M4 CQB Mk2
Secondary: Latino heat, TM Glock 17