A lot of the suggestions here are valid but it always helps to review the basics. Is the engine upright, inverted or sideways? Is the tank centerline at or below the height of the engine spraybar? Are you using a recommended prop ..... OS recommends up to a 13x7 but personally I think that's too much for this engine. 12x6/7 should be enough. Is your fuel fresh and have at least 10% nitro and 18% (or more) lube?

OK! Now go back to that 2 1/2 turns, start her up, leave the glow driver on and go to full throttle. She should run but be sloppy rich. Adjust the main needle to lean her out, pull the glow driver and then follow the break in instructions high speed for 10 seconds, back to low speed for ten seconds for a full tank (or two). These adjustments are done with the main needle, NOT the throttle. By the third tank you can open her up with the needle (but not at max rpm yet) and run as long as you want but it's then you adjust the idle with the low speed needle. Don't pinch the fuel lines or point the plane up and down. Just bring her to idle for a few seconds and then quickly advance the throttle. Coughing and slow acceleration mean the low speed needle is too rich, and abrupt stop means the low needle is too lean. Adjust it for a smooth transition to full throttle, readjust the high end needle and go fly! High end performance will improve through the first gallon of fuel and then you can optimize your prop and high end needle settings for best performance. Keep track of your rpm readings and you'll know when she's fully run in.