Seems that your belts are stretched and require ( tightening ) or replacement . The rate of throwing snow has nothing to do with rate of speed . The throttle full max will ensure the best possible distance snow can be propelled out the chute by the impeller fan from the anger . The gear selector 1 , 2 3 is rate of speed the transmission will propelled the blower itself . More Snow , the lower number is recommended . At 10 yrs old assume unit is 2 stage blower , not many single stage after 2001 .

snowblower forum said the issue is the fill rate of the chute. the faster i go, the more snow is rammed into chute/auger area and it impacts the amount of snow thrown. even though the impeller is running at same speed/rpm, the amount thrown is more. does not explain why the snow is thrown further. in my mind

The rule of thumb for any snowblower operation bud is not to exceed the rate of impeller or chute fan . The plugging occurs at the chute . The wetter the snow the slower you operate the blower drive . 1st gear is optimium during heavier snow conditions . Only 2 or 3rd gear during light fluffy snow . The throttle position is normally set to max unless snow conditions is very light or snow discharge distance is required to be very short . If your engine does not rev up on max then your governor is faulty. This is what governs the impeller speed . The gear selection does not affect the chute discharge only the speed the blower travels . If you have heavy or wet snow you use 1st gear selection and travel slow so the anger and impeller can effectively process the snow load ! Wet snow will be thrown less far and can clog the chute occasionally .