I thought I'd ask here before going to ORBX - there is quite a few of you scenery-guru's around here

So, as you know there are a lot of geothermal spots "simulated" around Rotorua and Taupo in ORBX NZNI. I've always found them unrealistic, way too big, and causing a mayhem to my performance (falls by 90%). I've been trying to find the actual effect file they used, but couldn't so far. I know it might be compiled into the bgl, but it really kills my Rotorua/Taupo experience. Any ideas how to get rid of them?
I'd really appreciate any help with this.
Cheers
Dan