I've got one myself (convertible) its like 260 hp. You got lucky too because 99 was the first year they did the hp jump. They went up 45 hp from 98 so its nice. Mine has exhaust, X-pipe, intake, diablo tuner, Nitrous. 345 hp w/o the Nos. 500 hp with it.
about 260 hp
The 1996 Ford Mustang GT was rated at 215 horsepower
Ford rated the 1993 Mustang GT at 205 horsepower
The 2001 Ford Mustang GT was rated at 260 horsepower
The 1997 Ford Mustang GT was rated at 215 horsepower
The 2005 - 2009 Mustang GT has 300HP.
The 2008 Ford Mustang GT has 300HP
A 2015 Mustang GT 3.7L V6 has a horsepower of 300 at 6500 rpm.
( 500 horsepower ) for the 2008 Mustang Shelby GT 500
The 2000 Ford Mustang GT has 260 horsepower
225 horsepower
260 Horsepower