why does my 2d platformer lags?

Hello Community, got this 2d plataformer, and the character is a vehicule, so Im using addforce to move it. i could swear it was working fine. but I dont know what happened now it lags when I press the horizontal axis keys. starts fine, after some seconds starts to lag untill it freezes, if I release the movement keys the game returns to be fine, but as soon as I press the either key (left or right) again it lags.
If I just move by pressing the boost button the game is totaly fine.
If I press the boost button when using the movement keys, the character just flys of the screen super fast like it had stored force in it.
help please, I have modified the script several ways and couldnt fix it.
this is the C# code:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PlayerStouss : MonoBehaviour {

public float speed = 6f , maxVelocity = 8f;
private Rigidbody2D myBody;
private Animator anim;
private float volLowRange = 0.5f;
private float volHighRange = 1.0f;

void Awake () {
	myBody = GetComponent<Rigidbody2D> ();
	anim = GetComponent<Animator> ();

}

// Use this for initialization
void Start () {

}

// Update is called once per frame
void Update () {
	
}
void FixedUpdate(){
	// this gets the imput of the player to jump
	PlayerMoveKeyboard ();{
	if (Input.GetButtonDown ("Jump"))
		Nitrous ();
		}
}
	// this gets the imput for movement
void PlayerMoveKeyboard(){
	float forceX = 0f;
	float vel = Mathf.Abs (myBody.velocity.x);

	float h = Input.GetAxisRaw ("Horizontal");

	if (h > 0) {
		if (vel < maxVelocity)
			forceX = speed;
		Vector3 temp = transform.localScale;
		temp.x = 1f;
			transform.localScale =temp;
					
		anim.SetBool ("StoussMoving", true);
		SoundManagerScript.PlaySound("StoussMoving");
				}
	else if (h < 0) {
		if (vel < maxVelocity)
			forceX = -speed;

		Vector3 temp = transform.localScale;
		temp.x = -1f;
			transform.localScale = temp;
		
		anim.SetBool ("StoussMoving", true);
		SoundManagerScript.PlaySound("StoussMoving");
	} 
	else
		anim.SetBool ("StoussMoving", false);
		myBody.AddForce (new Vector2 (forceX, 0));

	}

void Nitrous () {
	
	SoundManagerScript.PlaySound("StoussBoost");

	if (transform.localScale.x > 0)
		myBody.AddForce (transform.right * 8, ForceMode2D.Impulse);
	
		//myBody.AddForce (transform.up * 1 , ForceMode2D.Impulse);
	

	 if (transform.localScale.x < 0)
		myBody.AddForce (transform.right * -8, ForceMode2D.Impulse);
			    //myBody.AddForce (transform.up * 1 , ForceMode2D.Impulse);
}

}
thanks.

Check link: Unity - Manual: Profiler overview verify if is otimization this your game.