Even if you hit the perfect tuning for that car there I don't think you would break into the 1.30's ( assuming no corner cutting and penalties set to max). I think it has to do with Trial Mountain consisting of a lot of "medium" corners that most cars can take at around the same speed so there is not a lot to gain unless your car handles like crap to begin with.
I use trial Mountain more for testing a cars stability ( elevation changes ), I find Grand Valley gives a better overall idea of a cars weaknesses/ limits as it has more varied corners and a straight. Its a bit faster as a track. The slower the track the closer all the cars times tend to be so it becomes harder to define the better handling.
Hope this helps your quest somewhat?