Instead of having a 2.8 v6 or non h.o 305. It would have a 350 tpi or high output 305. It would have a different spoiler , suspension , and have formula stickers on the doors.
It's trim level. There are three trim levels for the Pontiac Firebird.
Firebird (base)
Firebird Formula
Firebird Trans Am
Firebird GTA (Third Generation Only) (it's to the Trans Am as the IROC-Z...