There's not really a such thing as a base level Trans Am, as a Trans is trim level of Firebird. Firebirds are the base level model, and they are powered by a 3.8L V6 putting out a disappointing 200hp. Next up is a Firebird Formula, which is cosmetically identical to the base level except for a Formula badge behind the front wheels, dual exhaust outlets (except on the '98 model), and its 5.7L LS1 V8, which is rated by Pontiac at 305hp ('98-'00) or 310hp ('01-'02). Although this is its claimed power rating, it is generally accepted that they are underrated, as some of the newer models dyno more than that at the wheels stock. Above the Formula is the Trans Am, which has the same engine and same power rating, but has a leather interior, raised rear deck spoiler, revised front fascia, fog lights and T-tops standard (although they were an option on the other models). There is also the Trans Am WS6, which has most notably, a more agressive hood and 17" wheels. Power is up to 320hp or 325hp (depending on year). They dyno about the same as regualr Trans Ams or Formulae. There is also the WU6 package, which makes the Trans Am into a Firehawk, which has different 17" wheels, a different hood, and various other upgrades and decorations. Horsepower is between 330 and 345hp depending on options (I believe, I don't know too much about Firehawks).