Check which Spur you're running. If it's the 81 tooth you might be slightly undergeared, in which case it will feel sluggish.
Which sintered rotors are you running in your X11's? The 14mm rotor need long gearing to feel good, otherwise run a thinner one, like a 13mm or 12.5mm. These will give you less torque and more top end.
The 4.5 is a bit useless for offroad as it is just way too quick with lipo. In fact it isn't recommended at all with lipo as it will rev until the rotor shatters...
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