Make a new txt file. Copy in this code. Click on Save As. Yourname.lua 
Open the meta file in notepad and write in      
<script src="Yourname.lua" type="client" /> 
 
Just works when you are making a race map (DM,DD,Race) 
You have to test with race too. Not working if you just press F5. 
Change the X,Y,Z to your cords. 
You can change the  
Multiplier = 1.5 
 how much you want. (Dont go higher then 5.0) 
Do not change anything under  
fuction SpeedBoost (player) 
 
function start() 
    SpeedBoost = {   
                createMarker (X,    Y,  Z,        "corona",       5,    60,     255,    100,    255 ), 
            }                                                         
  
end 
addEventHandler ( "onClientResourceStart", getResourceRootElement(getThisResource()), start ) 
                                   
  
Multiplier = 1.5 
  
function SpeedBoost (player) 
    if player ~= getLocalPlayer() then return end 
    if getElementType(player) == "player" then 
        if isPedInVehicle ( player ) then 
            local car = getPedOccupiedVehicle(player) 
            if getVehicleController(car) == player then 
                speedx, speedy, speedz = getElementVelocity ( car )  
                speedcnx = (speedx*Multiplier) 
                speedcny = (speedy*Multiplier) 
                speedcnz = (speedz*Multiplier) 
                setElementVelocity ( car, speedcnx, speedcny,speedcnz ) 
                fixVehicle(car) -- fixes the vehicle 
                playSoundFrontEnd(46) 
            end 
        end 
    end 
end 
addEventHandler ( "onClientMarkerHit", getResourceRootElement(getThisResource()), SpeedBoost )