The heat of 914 spark plugs is generally a good all around plug for everyday use and even autocrossing. Simply put, hotter plugs burn hotter and colder plugs burn colder which relate to the amount of heat transfered from the plug to the head. High compression full throttle race engines will a a slightly colder plug than a comparitive street engine since hot plugs can cause preignition, etc. Check out the two links below to get some more info on plugs. Good luck.
http://www.clubplug.net/cross.html
http://www.softcom.net/users/magers/html/ngk_lookup.html