Hello Huison.
For my part (I think it's the same problem for all the 170DZ just outside the factory) my moter was very very lean and I couldn't pass the 1/3 gaz without amazing vibration and danger.. (one time the propeller has been unscrew from the engine...)
So Mr Carrier and Papaone from the forum explain me that the motor was too lean and I must turn the screw clockwise and open the turn end.
After it I have try this advise screwing the reg 2 turn(before it I haven't touch to the factory setting so I have put 2 turn more than the factory setting) and open the turn end at 2.5 turn (from the totally closed). my screw reg is 1.5mm inside the end of the reg.
For my part The YS with myoil mix work perfectly but I think for the cool power you can test for a first test to give only 1 turn to the reg.
I hope could you.
Don't hesitate to contact me by MP or email.
Regards.