No. I assume cat to straight pipe would be a negligible change if any. I'm just shitting on you for the "hurr durr it likes them there back pressure" comment.
Dick.
If I say something dumb, I'll own it though. My limited experience with this is that stock V8's don't seem to benefit from ditching the cat and leaving everything else the same. It might add better flow in the higher revs but the low to mid rev torque seems to suffer, be it from loss of scavenging or back pressure or whatever. I'm not an engine tuner.
But this is a Ford V10, I'm already going to be welding on the Y-pipe for the SPD kit, and it's no additional work either way. I'm 50/50 between trying it out without a cat.