I have a 1996 7.3 powerstroke and when it is cold out side it sometimes like to lose power and some RPM's. Ill give it a little gas and it feels like its missing air and making a, for a lack of a better term, sucking sound. but when I put the pedal to the floor it picks back up and takes off. I replaced the fuel and air filter on it and it continues. Im from west Texas and yesterday it was 80 outside and it was running like a champ, but today it was 35 and it was being slugish. Any ideas what it is?

 

1994.5 - 1997 7.3L Power Stroke Diesel - Ford Truck Enthusiasts Forums Here is a link to the page for your engine, probably better to ask the guys there.
Good luck.