Per the FMF website, there is no such thing as an FMF Turbine Core SST...
"Turbine Core II Spark Arrestor™ The ultimate choice when comes to remaining legal and not adversely affecting power. "
As far as the SST-labeled product they do make, it does not sound like it applies to a woods bike like your EXC.
" SST Pipe: 2001 Targeted towards outdoor moto and higher speeds, the FMF SST pretty much mirrors the stock power in only one area- roll-on. Then all hell breaks loose as the SST enhances the mid range and bolsters the peak performance on the KTM 250."
FWIW,