It seems like the cam to me. Your tq curve just doesnt look as flat as most I see, I don't really understand why. As far as that dip, my dyno graph shows one in the exact same place as yours around 4200 rpm. That's kinda strange.
https://ls1tech.com/forums/dynamometer-results-comparisons/280904-fms-f11-stage-ii-lsx-90mm-results.html

 

maybe it has to do with the really agressive lobes both Futural and tsp use? who knows...

 

Futral doesn't use "aggressive" lobes. They're cam motion lobes, which aren't anywhere near "aggressiveness" of the comp lobes that TSP uses.

 

arent their lobes inbetween comps xe-r and xe lobes? thats what i read on here a while back

 

Until recently, some of the TSP grinds had some lazy lobes (like the 231/237 I use) using lunati cams.
From what I read on their 233/239 thread, they've implemented some more aggressive lobes in their newer grinds, but I don't know if they're like XER lobes. Would be best to ask them directly.

 

that dip in alot of cams sure is wierd.