(HELP) ¿InputEnded Don't Working? Sonic's Boost

I Make My Own Sonic's Boost But Have's Don't Working

Problem: InputEnded Sometimes Can't Execute

Example: (http://www.youtube.com/watch?v=VcCIbcnKsbg)

I Need Help, Because I'm Beginner & I Don't Know Much Scripting

My Boost Script:

local uis = game:GetService("UserInputService")

local player = game.Players.LocalPlayer

local char = player.Character

local humanoid = char:WaitForChild("Humanoid")

local sound1 = char:WaitForChild("Torso").SoundGroup.Sound1
local sound2 = char:WaitForChild("Torso").SoundGroup.Sound2
local sound3 = char:WaitForChild("Torso").SoundGroup.Sound3
local sound4 = char:WaitForChild("Torso").SoundGroup.Sound4

local RunService = game:GetService("RunService")

uis.InputBegan:Connect(function(input)
    if input.KeyCode == Enum.KeyCode.LeftShift and humanoid.WalkSpeed == 50 then

        mo = char:WaitForChild("Mo")

        mo.Disabled = true

        char.Humanoid.WalkSpeed = 300

        local blur = game.Lighting.Blur

        blur.Size = 10

        local bloom = game.Lighting.Bloom

        bloom.Threshold = 0.8

        bloom.Size = 56

        sound1:Play()
        sound2:Play()
        sound3:Play()
        sound4:Play()

        game.Workspace.Camera.FieldOfView = 80

        gui = Instance.new("ScreenGui",game.Players.LocalPlayer.PlayerGui)

    local image = Instance.new("ImageLabel",gui)

        gui.Name = "Effect"

        gui.Enabled = false

        image.Name = "Wave"

        image.Image = "rbxassetid://11528455881"

        image.BackgroundTransparency = 1

        image.ImageTransparency = 0.3

        image.Size = UDim2.new(0.09,0,0.15,0)

        image.Position = UDim2.new(0.444,0,0.404,0)

        gui.Enabled = true

        image:TweenSizeAndPosition(
            UDim2.new(1.727, 0,2.879, 0),
            UDim2.new(-0.364, 0,-0.94, 0),
            Enum.EasingDirection.InOut,
            Enum.EasingStyle.Quad,
            0.3,
            false
        )

        wait(0.05)

        game.Workspace.Camera.FieldOfView = 90

        wait(0.05)

        game.Workspace.Camera.FieldOfView = 100

        wait(0.01)

        bloom.Threshold = 2

        bloom.Size = 24

        wait(0.105)

        blur.Size = 0

    end
end)


uis.InputEnded:Connect(function(input)
    if input.KeyCode == Enum.KeyCode.LeftShift then
        if humanoid.MoveDirection.Magnitude == 0 then

            mo.Disabled = false
            char.Humanoid.WalkSpeed = 50
            sound1:Stop()
            sound2:Stop()
            sound3:Stop()
            sound4:Stop()

            game.Workspace.Camera.FieldOfView = 100

            wait(0.001)

            game.Workspace.Camera.FieldOfView = 95

            wait(0.001)

            game.Workspace.Camera.FieldOfView = 90

            wait(0.001)

            game.Workspace.Camera.FieldOfView = 85

            wait(0.001)

            game.Workspace.Camera.FieldOfView = 80

            wait(0.001)

            game.Workspace.Camera.FieldOfView = 75

            wait(0.001)

            game.Workspace.Camera.FieldOfView = 70
            char.Humanoid.WalkSpeed = 50
            gui:Destroy()
        end
    end

end)

Momentum Script (Don't Mine) = Variable: Mo

local MaxSpeed = 50
local Multiplier = 1.07
local BaseSpeed = 2

while true do wait()
    if script.Parent.Humanoid.MoveDirection == Vector3.new(0, 0, 0) then
        script.Parent.Humanoid.WalkSpeed = BaseSpeed
    else
        script.Parent.Humanoid.WalkSpeed = script.Parent.Humanoid.WalkSpeed * Multiplier
        if script.Parent.Humanoid.WalkSpeed >= MaxSpeed + 1 then 
            script.Parent.Humanoid.WalkSpeed = MaxSpeed
        end
    end
end

Bye.r