Reset speed after a specified time

Im currently creating a 2d side scrolling game. When the character (which is a bike) hits the boost he speeds up, but I cant seem to get him to slow down again. I should point out that the character is actually immobile and the environment around him is moving (I did this because I wanted to create a parallax effect with the background). When he hits the boost, the environment speeds up. The codes something like this:

void OnTriggerEnter(Collider theCollision){

if(theCollision.gameObject.name == "Token Boost") {
 
Debug.Log ("Hit the item boost!");
Destroy (theCollision.gameObject);
foreach(GameObject go in GameObject.FindGameObjectsWithTag("environment")){
    go.GetComponent<parallax>().Speed *= 0.5f;
}     
}

If you could help me out id greatly appreciate it

Write a new method that slows it back down…essentially the methods would be identical to the ‘foreach’ code above, but would would change the speed the opposite way. Then right after the last like line in the code above you insert:

Invoke("SlowBackDown, 5.0f);

Where ‘SlowBackDown’ is the name of the method, and 5.0 is the time in seconds in the future you want the method to be called.