i'm using the ST plug "S8I"..which is a long reach and is also the one that comes installed in the TH.75.
http://www2.towerhobbies.com/cgi-bin...p?&I=LXGWY5&P=

Flyboydave also uses the K&B1L which is also a long reach, and i've tried it as well, and it works perfect with this engine, but you have to get them from K&B.

http://www.mecoa.com/acc/glowplug/glowplug.htm

i've tried the Tower and the OS #8 which are short reach plugs.......both changed the idle transistion for the worse.

the TH .75 heads are set up for long reach plugs.........makes no sense to use short reach plugs.