AC blower strange problem

My ac blower works on all speeds. My question is when its on high speed and you are sitting its fine when you start to accelerate down the road it only blows like if it was on low speed. then after a few minutes or so it will blow normal again does anyone know what the problem might be? Thanks

By the way its a 98 model

It sounds like you need to check the vacuum controls to the duct system. When the main control starts to go out you may see a decrease in air when you accelerate. The key is when you accelerate, the vacuum to your engine increases and causes the accessories to operate. When this happens it will cause vents to shut off or partially close acting like the fan is not working properly. You need to check the vacuum hoses to the engine as well as to the vents. Should find the connection to them under the dash or behind the control panel.