1995 Ford Bronco acceleration

Ok ill try to paint this very clear, tho it never happens in the city/normal everyday driving, I went on a road trip the other week and on hills/steep inclines I would loose power in my accelaration. My rpms would fire up to 3000 but I couldnt keep it past 55/60 mph. Also the temp would heat up alot but not overheat. Any ideas? Ive read everything from maybe the cat to dirty air filter, all of which I been starting to go thru now.