I don't know how much the elevation affects it. I'm not going to sugar coat it. 15's @ 93 mph is really slow. However, it seems to me that you could reasonably shave .5 second off your 60ft time which is worth about a second on the big end. So you could probably see 14's.
What's your HP? Mine makes 314 at the wheels and goes 11.70's in full street trim. And I don't make it into 4th gear either.