You've probably already seen this, but here's a little explanation of glow plugs. http://www.osengines.com/accys/glowplugs.html
http://www.osengines.com/accys/choosing-glowplugs.html Personally I used the #8 for my t-15 when I had it in there, and now with the s-25 I use the A5. All I do is bash and do high speed runs, no racing because I don't want to have to drive an hour or more to get to a track and practice. There used to be a couple tracks here, but I guess the r/c world is'nt popular enough here as they were shut down well before I ever knew of them.