I'm not sure how they compare to the Toomey's as I've never run a set of T-5's. The 916 system seemed to open up the midrange and top end a lot on my bike. The low-end seems about the same. I think most people on the HQ classify these as a decent all around pipe. The center mount is sweet. Reminds me of the Ducati exhausts.
As an aside there are pipes that are known for adding more low end power, such as the Dynoport 2 into 1, or the FMF Fatty or Gnarly, however, I think that the consensus is that these do so at the expense of the crazy top end that the Banshee is legendary for.