I believe the manual gives a range in ratios, not percentages. At 25 to 30% you are running a lot of oil!! Try a new mix of 32-1. That's 4 ounces of oil to 1 gallon of gas. I'm certain that if you are using a 25-30% ratio it's a very large part of your problem.

Next is carb tuning. It has to be done every time you change oil ratios and prop sizes. I think you might like a 22-8 a little better. My personal preferences do not include Xoar or Vess. For a good baseline prop try Menz or NX.

Using a 32-1 ratio your engine will take a few gallons (about 5 hours of running time) of fuel before it has fully broken in.