105? That's insane! What equipment does that line use?
Not really. The Empire corridor runs with General Electric P32ACDM Genesis dual mode diesel/electric locomotives and will hit speeds of up to 110 between Spuyten Duyvil and Schenectady. The standard Northeast Regionals do up to 125 along the corridor between Boston and Washington. The Keystones will hit speeds of up to 110 between Philly and Harrisburg, and will hit 125 as they blast along the Corridor through New Jersey.
The Silver Meteor, Silver Star, Crescent, Palmetto, and Regional 66/67 and Carolinian will hit 110 between New York and DC.
The Superliners and Surfliners are built for 100 mph operation. The Heritage cars and Viewliners are built for 110. The Amfleets and (currently defunct) Turboliners are built for 125. The Horizons are theoretically rated for 125, but in practice are never run faster than 110- they have demonstrated considerable instability faster than that (There is a reason they were quickly removed from Corridor service on the New York-Washington trains and are relegated to Chicago trains whose cold temperature they are also not suited to). The Acela Express trainsets are rated for 165 mph, but are never operated above 150 in revenue service.
Ever heard the song City of New Orleans? Well the train they are referring to, a crack day train, hit 100 mph on ICs light-weight rail using old and decrepit equipment. The train they currently run used to be called the Panama Limited by Amtrak- although it bears no resemblance to THAT train either.
HOWEVER, as far as I know, and I'm sure George Harris will either back me up or correct me, the Sunset Limited is never operated on track faster than 79 mph rating. If you are doing what you say you are doing, your engineer is being enthusiastic.