Remove power up?

Hello,

I have an Powerup system, Players can buy those with points and it will add you that amount of "Number" there. Example Anti Gravity. If you buy it it will add +4 there. At first you're gravity is 100% and if you buy it will take -4% away always. My question is: If player has Gravity Coil in BackPack or in hand

if Player.Backpack:FindFirstChild('GravityCoil') or Player.Character:FindFirstChild('GravityCoil') then

Then how could I change the Powerup (Gravity) to 100%? If he doesn't have it anymore, then it goes back to where it was.

Power Up code:

if Points.Value >= 150 then
Points.Value = Points.Value - 150
Powerups[Player]["AntiGrav"] = Powerups[Player]["AntiGrav"] + 4
GravityUp.Text = "Gravity -4% for 150 points (" .. 100 - Powerups[Player]["AntiGrav"] .. "%)"
UpdatePowerUps(Player)
end

I still need help with that. More code:

pcall(function()
local Torso = Player.Character.Humanoid.Torso
local AntiGrav = Torso:FindFirstChild("BodyForce") or Instance.new("BodyForce")
AntiGrav.force = Vector3.new(0, GetMass(Player.Character) * 196.2 * Powerups[Player].AntiGrav / 100, 0)
AntiGrav.Parent = Torso
end)

Also, that

if Player.Backpack:FindFirstChild('GravityCoil') or Player.Character:FindFirstChild('GravityCoil') then

That one doesn't seem to work at all. I did if he has GravityCoil, then it will print("Has the item") but it didin't print it. Could someone help