Convert current rigidbody velocity to transform.forward

I'm tuning my drift mechanic so that when the drift is released, the player gets a huge burst of speed in the direction they are currently facing. As is, it does grant a huge burst of speed, but the momentum from previous forces still apply and the player moves like they're on ice.

Here's my code:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class playerControl : MonoBehaviour
 {
     public float speed;
     public float accel = 10.0f;
     public float topspeed = 15.0f;
     public float turnSpeed = .35f;
     public float driftSpeed = 2f;
     public float driftDrag = 5f;
     public float driftBonus;
     public float jumpCharge = 1.0f;
     public bool drift;
     public bool grounded;
     public bool breaking;
     private Rigidbody rb;
     private float turnDir;
     [SerializeField] private float driftLock;
     // Start is called before the first frame update
     void Start()
     {
         rb = this.GetComponent<Rigidbody>();
     }
 
     // Update is called once per frame
     void Update()
     {
         speed = rb.velocity.magnitude;
         Inputs();
         //Regulate Speed
         if (speed < topspeed+1 && !breaking && grounded)
         {
             Accelerate();
         }
         else if (speed > topspeed)
         {
             breaking = true;
         }
         //Drift Function
         if (drift)
         {
             Drift();
         }
         breaking = false;
     }
 
     private void FixedUpdate()
     {
         if (breaking)
         {
             Slow();
         }
     }
 
     private void Inputs()
     {
         //Turning
         if (Mathf.Abs(Input.GetAxisRaw("Horizontal")) > .05)
         {
             transform.Rotate(0, Input.GetAxis("Horizontal") * turnSpeed, 0, relativeTo: Space.Self);
             turnDir = Input.GetAxisRaw("Horizontal");
         }
 
         //Drifting
         if (Input.GetKeyDown(KeyCode.LeftShift) && Mathf.Abs(Input.GetAxisRaw("Horizontal")) > .05 && grounded)
         {
             drift = true;
         }
         else if (Input.GetKeyUp(KeyCode.LeftShift) && grounded)
         {
             drift = false;
             //Adds boost
             if (5 <= speed && speed <= topspeed)
             {
                 rb.AddForce(transform.forward * ((topspeed/1.5f) * (driftBonus/10)), ForceMode.Impulse);
             }
             else
             {
                 rb.AddForce(transform.forward * (driftBonus/10), ForceMode.Impulse);
             }
             driftBonus = 0;
             driftLock = 0f;
         }
         //Jump Charging
         if (Input.GetKey(KeyCode.Space) && grounded)
         {
             //charge jump
             if (jumpCharge < 3.5f)
             {
                 jumpCharge += .1f;
             }
             else
             {
                 jumpCharge = 2;
             }
             //slow speed
             if (speed > 3)
             {
                 breaking = true;
             }
             else
             {
                 breaking = false;
             }
         }
         //Jump Release
         else if (Input.GetKeyUp(KeyCode.Space) && grounded)
         {
             rb.AddForce(transform.up * (2 * jumpCharge), ForceMode.VelocityChange);
             jumpCharge = 1f;
         }
     }
 
     private void Drift()
     {
         //Lock Drift Direction
         if (driftLock == 0f)
         {
             driftLock = turnDir;
         }
         //Modify Drift Intensity
         if (Input.GetAxisRaw("Horizontal") == -driftLock)
         {
             driftLock = driftLock + (.25f * Input.GetAxisRaw("Horizontal"));
         }
         else if (Input.GetAxisRaw("Horizontal") == (4/3) * driftLock)
         {
             driftLock = (4/3) * driftLock;
         }
 
         //Drag
         if (speed > 1)
         {
             rb.AddForce(-transform.forward * (speed * driftDrag));
         }
         //Drift
         transform.Rotate(0, driftLock * driftSpeed, 0, relativeTo: Space.Self);
         //Boost
         if (driftBonus <= 20)
         {
             driftBonus += 1f;
         }
 
         if (speed < 3.0f)
         {
             drift = false;
             driftBonus = 0;
         }
 
     }
 
     private void Slow()
     {
         //Reduce to Topspeed
         rb.velocity = rb.velocity * .95f * Time.deltaTime;
         speed = rb.velocity.magnitude;
     }
 
     private void Accelerate()
     {
         //Increase to Topspeed
         speed = rb.velocity.magnitude;
         if (speed < topspeed)
         {
             rb.AddForce(transform.forward * accel);
         }
         else
         {
             rb.velocity = rb.velocity.normalized * topspeed;
         }
     }
 
     private void OnCollisionStay(Collision collision)
     {
         if (collision.collider.gameObject.layer.Equals(8))
         {
             grounded = true;
         }
     }
 
     private void OnCollisionExit(Collision collision)
     {
         if (collision.collider.gameObject.layer.Equals(8))
         {
             grounded = false;
             drift = false;
             driftBonus = 0;
             driftLock = 0f;
         }
     }
 }

The section that handles boosting is Lines 66-85:

 //Drifting
         if (Input.GetKeyDown(KeyCode.LeftShift) && Mathf.Abs(Input.GetAxisRaw("Horizontal")) > .05 && grounded)
         {
             drift = true;
         }
         else if (Input.GetKeyUp(KeyCode.LeftShift) && grounded)
         {
             drift = false;
             //Adds boost
             if (5 <= speed && speed <= topspeed)
             {
                 rb.AddForce(transform.forward * ((topspeed/1.5f) * (driftBonus/10)), ForceMode.Impulse);
             }
             else
             {
                 rb.AddForce(transform.forward * (driftBonus/10), ForceMode.Impulse);
             }
             driftBonus = 0;
             driftLock = 0f;
         }