TORX is special fastener developed by and for GM (I think) which is used seemingly at random throughout their vehicles in place of the (stupid and strippable) Phillips screws of yesteryear. The TORX heads are very strong and very tough to strip but they do require the corect bits to undo them or tighten them.
If you aren't sure what they look like check out the little screws which hold on the bezel (plastic panel) around the radio. There are about 4-6 TORX head screws holding it on and they are visible without removing anything at all. They look a bit like an Allen head (or more correctly a socket head) but they have a little extra indentation at each corner. If you stare are one they are quite unmistakeable.
There are a range of TORX sizes from very tiny (say about T-5) up to really big like T-55 or T-60. I must admit that I don't know what the numbers mean - perhaps millimetres across the flats? Anyway - you need the correct size to deal with them and you might as well invest in a set if you are going to work on a Fiero.
From: Peter Frise