Hi!
As has been said!
Sounds like a too rich idle setting! Remember that you always set the needles by ear! Not in how many turns the needle has!
In an ordinary sport engine that you have an OS 8 or Enya 3 glow plug is a good choice! There are other plugs too that are as good like the Nova Rossi 4 or 5 or Rossi 3 or 4, but the Enya 3 and OS 8 are the old -stand-by:s that are easy to find in most hobby shops!

Do use 5%-10% nitro! That's what all engines likes! 15% is overkill and more nitro and your engine will probably experience bad running behavoir (wrong ignition point) due to too much nitro!