I was removing the cooling system for cleaning and noticed a hole between the fan and the radiator on the GPU # 1 that disperses the air flow.
It can solve easily by applying a trimming in PVC, or any other material, closing the hole, avoiding the dispersion of air. (Gain -4 ° C)
I also applied the heat sink directly on the block of the GPU and CPU.
CPU (gain -2°C)
GPU (gain -3°C)
I also modified the backcover, by increasing the air flow (Gain -2 ° C)