Those are 2 dino sheets right 1 flywheel dyno and 1 rear wheel dyno? They both show the same thing a rythmatic dip and rise! So the if that's the case, the tires drive train etc is not the cause of the dip in power!!
Most dyno runs are at least 3 , One cold eng run, one hot run, and one second hot run to check data against (best run of the 2). There is also data smoothing that takes tire & converter slip and throttle into consideration in printout on some dynos smoothing out the curve but some operators don't use it and read raw data!
Tightening tires down tighter on rollers after first run will drop power readings drastically on a second run! Tire pressure and any drag in drive train is very impotent as Hcomton said! Fluid temps must be at operating temps! Car must be in 1to1 final gear for a good reading.
Your torque dropped right off at 5000 rpm and came up again till 5500 and then dropped off steadily from 5000 on!
Valve train harmonics are whats sticking in my mind as the cause! When the resonance comes to its peak at 5000 rpm and as torque is reduced at 5300 rpm the resonance levels out and torque starts to resume momentarily till the torque band starts dropping off! I would check the valve train, maybe girdle it, push rods could be resonance flexing, Could be cam flex, ETC
Resonance can be through the whole rpm range and have a slow undetectable rhythm at low rpm with not much affect but as rpm and load build: the rhythm increases its wave cycle till it reaches a peak and something physically gives Like push rods, springs, rocker studs, cam!they will flex and absorb the harmonic distortion momentarily like a damper affect and then level out till the resonance begins again repeating the cycle!