Mine is a 2000 GT Premium w/o traction control then?... you got me thinking here... I've always wondered what that small round hole in front of the shifter is... I got the car second hand... I will take a pic and post it here so you can shed some light...
Your '99 got it as an option? or it is always on?
if its got a conspicuous hole there in front of the shifter, it might be where the switch was. post a pic and i'll let you know, or ill post a pic of mine later.
as far as it being an option, its just always on by default tune. As soon as it feels excessive wheel spin, it'll automatically apply brakes and cut fuel. However, the switch that is in front of the shifter allows me to turn off TC at any time, so it doesn't apply brakes or cut fuel when i don't want it to. I press the button, and "OFF" is illuminated, so its off lol Once i turn the car off and back on, TC is automatically enable again until i press the switch again. The light on the dash should only come on when TC is in operation, say when you do a little peel out or hit some water and spin a bit and it applies brakes and cuts gas, which bogs it down noticeable amount.
mine is a 99 GT, i guess premium, not sure, came with Mach 460 system but not much else that i know is an option
also, TC can be permanently disabled through handheld tuner IIRC, so that might be why you've never gotten the light to turn on or TC to activate if you did have it before.