BIG-IP Virtual Ed. Capped at 115mbits Via Iperf Tests

My first guess is that the traffic distribution through the tunnel is not optimal. 115mbps will workout as 225mbps bi-directional, and if your instance has 4 tmms, then this may line up with why you observe 1000mbps when you connect directly (225 x 4 ~= 900). That is just an educated guess, but that is a very possible cause of the bottleneck:

all the traffic is hitting only one TMM and that TMM gets maxed out (it is tied to a single CPU core) and you can't go faster than that.