[Eljaro]

if you can not get .80 air jets you can take some of the larger air jets you have laying around, drill them larger on a lathe, make yourself brass plugs, plug them up and drill them new with a .80mm drill.You can also plug them with tin solder and drill them again to .80mm.
Do you have the dyno sheet on how the curve looks like with the F14 tube?
I do not know what the F15 will do. But from what you say right now the F14 is the best combination with only the lean top end to be taken care of. The only way to correct that now is with the air jet.Try the smaller air jet before doing anything else.
If you can get a smaller drill than .80, say 0.50 I would try that too. You can always keep enlarging the hole if you overshoot on top end richness.