Chicago, I agree that you need a little more oil content for the motor but don't go over 12% oil and do run 30% nitro. When I first got into the hobby I ran the Trinity Monster Fuel with 16% oil and it was terrible. I couldn't sustain a good tune and it kept getting bogged down. I then went to White Lightening 30% with 8% oil and it ran great but the engine got to hot and I didn't think I was gaining anything by richening out the engine. I have found the middle of the road is best with Trinity 30% with 12% oil. I believe O'Donnell also has excellent fuel.
I am concerned that your LHS would tell you that it is okay to run without the carb insert. DON'T DO THIS!!
You need the insert for two reasons. It helps keep the air cleaner hooked on and the design of the insert helps increase velocity of air flow in the carb due to the funnel effect. You may also damage your engine doing this and I wouldn't think you would gain any power.
Anyway best of luck to you and let us know how things are going.
Rockman