Both myself and my housemate own this and both experience the above mentioned issue. We both run GT 640's. I run a brand new i7 4820k (NOT o/c'ed) with currently 6G Ram. My housemate runs a new I3 with 4G Ram. I run Win7 Pro 64bit and my friend Win8 64bit.
Now, I recall having a very similar issues in the beta of Trials Evo Gold. I have tried absolutely everything within my IT knowledge to resolve it in Fusion, and have had minimal success. The only thing that does work effectively for us, is lowering resolution. Even doing this, some parts of some tracks slow down. We are at a point where the resolution looks terrible, but the game plays reasonably well.
If I remember correctly, TEG had the advanced effects option, which I always left off - the game just ran better on my system without the option on. Fusion does not have this option, so, I went looking at the graphics config file in documents. There is not much in there -
<?xml version="1.0"?>
-<UserGraphicConfig version="1.0">
<Window fullscreen="true" height="768" width="1024"/>
<GPU vsync="false"/>
<PostEffect fxaa="-1"/>
<VideoOption frame_rate="false" environment_quality="0" shadow_quality="1"/>
</UserGraphicConfig>
I have been into my Nvidia control panel and turned all the standard stuff off that I think may affect things, like AA, Vsync, etc. No amount of tweaking in Nvidia for this game seems to have an effect. I looked at the in-game video options and found it strange that I can't turn shadows off completely. So my next step is to try changing the shadow quality in the above config. As you can see, the settings are already extremely minimal for troubleshooting.
I will post back shortly if I have any success. Keep the input coming all - this good series can be great if we can nut out the glitches ;)


