I did not recommend a TGF someone else did. If I made a recommendation it was just to use a 5
however a 5 cold is what I use. I believe stefan was referring to the number 5's as the hottest plugs of their kind. (generally an accurate statement) and yes the TGF is a cold 5, yes the TC is a hotter 5.
Personally I agree with Stefan and use the TGF. Heres why but it is my personal reason. The TC for me suffers harmonic failure in engines I build, so therefore I cant use them successfully unless its below 50 degrees on 30% max fuel.