My riding mower is a 22hp 3 blade 46" width. When it had old blades, I had to slow down in thick spots so it'd cut evenly and I could feel it working harder. When I put in new gator blades, I could go through those full speed with ease. Nothing else was changed in my mower, only the blades.
If your blades are dull/old, try new gator blades.