Just about got this thing dialed in now. the problem I was having in the past was that, according to the manual, you should open the high end needle 4-5 turns during break in. this caused an overly rich setting that made the engine bog down at higher throttle settings. I tuned it, still rich, to turn a 20/8 Zinger Pro at about 6800 RPM's. the manual says to break in at 6k. a few seconds after I throttle down and kill the engine, I can see smoke. I used 5% nitro 20%oil for the first gallon, and Cool power FIA fule for the second. the smoking occured with both types of fuel equally the same. is this normal or should I run it even more rich?

You don't need that much oil with that engine. 15% oil like in a 4 stroke fuel is fine.

If you take a look at the muffler you will likely see alot of discoloration from burnt fuel/oil. The smoke may be from that. As far as richening it or not - Let the motor warm up and then set the needle for peak RPM. Richen it until the RPM drops 200 - 300. That should get you real close. One thing to consider doing when setting the needle as described is to do so without much fuel in the tank, if you're not runing a regulator or pump. Reason for not having much fuel is that in a large tank, such as a 24 oz, the weight of the fuel supposedly tends to "push" the fuel but you loose that affect when the fuel burns off, possibly leaning the mixture.

As far as the fuel/oil - Use whatever your manual says. Seems like I recall it saying not use less than 18% oil and definitely not straight synthetic.

I know this wasn't part of your question, but you'll notice a jump in performance if you swap the prop for something else. You can get an NX 20x8 for $19.00 from AirWild Hobbies (no, I'm not affiliated in any way). It pulls and brakes well.

Dan