diff --git a/src/helpers/promotions-helper.js b/src/helpers/promotions-helper.js
index a5d94789b..1689d9550 100644
--- a/src/helpers/promotions-helper.js
+++ b/src/helpers/promotions-helper.js
@@ -1,6 +1,7 @@
 import store from "@/store";
 import { storeActions } from "@/constants/store-actions";
 import { partTypeStrings } from "@/constants/part-type-strings";
+import { deepClone } from "@/helpers/object-helper";
 import baseMixin from "@/mixins/base-mixin.js";
 
 export const promoPartNumberStrings = {
@@ -126,6 +127,31 @@ export function getPromosThatMatchLineItemsOnOrder(promos, lineItemsOnOrder) {
     return matchingPromos;
 }
 
+// Returns the vaps that the provided <promos> requires to be on the order to satisfy
+//  Items that are already in <lineItemsOnOrder> will not be returned
+export function getVapsThatNeedToBeAddedToSatisfyPromos(
+    promos,
+    availableLineItems,
+    lineItemsOnOrder
+) {
+    const clonedVaps = deepClone(lineItemsOnOrder.vaps ?? []);
+    const promosWithAddableVaps = getPromosWithAddableVaps(promos);
+    if (promosWithAddableVaps.length) {
+        const matchingLineItems = getLineItemsThatMatchPromos(
+            promosWithAddableVaps,
+            availableLineItems
+        );
+        // Check if matching items are already in the order
+        const idsOfVapsAlreadyInOrder = clonedVaps.map((lineItem) => lineItem.id);
+        const vapsToAddToCart = matchingLineItems.filter(
+            (lineItem) => !idsOfVapsAlreadyInOrder.includes(lineItem.id)
+        );
+        return vapsToAddToCart;
+    } else {
+        return [];
+    }
+}
+
 export function shouldStripPromoQueryString(fmgPageQueryValue) {
     return pagesToStripPromoQueryStringFrom.includes(fmgPageQueryValue);
 }
diff --git a/src/layouts/payment-method/add-vaps-modal-buttons/add-vaps-modal-buttons.vue b/src/layouts/payment-method/add-vaps-modal-buttons/add-vaps-modal-buttons.vue
index bb378c619..b4fa7a3b0 100644
--- a/src/layouts/payment-method/add-vaps-modal-buttons/add-vaps-modal-buttons.vue
+++ b/src/layouts/payment-method/add-vaps-modal-buttons/add-vaps-modal-buttons.vue
@@ -97,7 +97,11 @@ export default {
             this.$refs[modalName].closeModal();
         },
         addRainDefenseToCart(modalName, part) {
-            this.currentCartItems.vaps.push(part);
+            // Clone vaps array, then replace this.currentCartItems.vaps with it at the end
+            //  in order to successfully trigger parent's watcher
+            const clonedVaps = this.currentCartItems.vaps.slice(0);
+            clonedVaps.push(part);
+            this.currentCartItems.vaps = clonedVaps;
             this.closeModal(modalName);
             const message = this.getRainDefenseAddedMessage();
             this.$emit("added-to-cart", {
@@ -133,19 +137,23 @@ export default {
                     this.selectedWipers = ["REAR"];
                 }
             }
+            // Clone vaps array, then replace this.currentCartItems.vaps with it at the end
+            //  in order to successfully trigger parent's watcher
+            const clonedVaps = this.currentCartItems.vaps.slice(0);
 
             itemsForCart.forEach((type) => {
                 if (type === wipersOfferedStrings.FRONT) {
                     part.frontWiperLineItems.forEach((part) => {
-                        this.currentCartItems.vaps.push(part);
+                        clonedVaps.push(part);
                     });
                 }
                 if (type === wipersOfferedStrings.REAR) {
                     part.rearWiperLineItems.forEach((part) => {
-                        this.currentCartItems.vaps.push(part);
+                        clonedVaps.push(part);
                     });
                 }
             });
+            this.currentCartItems.vaps = clonedVaps;
 
             this.closeModal(modalName);
 
diff --git a/src/layouts/payment-method/payment-method.vue b/src/layouts/payment-method/payment-method.vue
index 8a5f3a21d..6e87235b0 100644
--- a/src/layouts/payment-method/payment-method.vue
+++ b/src/layouts/payment-method/payment-method.vue
@@ -88,7 +88,8 @@ import { paymentMethods } from "@/constants/payment-method-constants";
 import { experimentSettings } from "@/constants/experiments";
 import {
     revalidatePromosAndValidateNewPromo,
-    getAddableVapsFromAvailableLineItems,
+    getPromosWithAddableVaps,
+    getVapsThatNeedToBeAddedToSatisfyPromos,
 } from "@/helpers/promotions-helper";
 import { queryStrings } from "@/constants/query-strings";
 import { getQuerystringParameter } from "@/helpers/querystring-helper";
@@ -177,7 +178,9 @@ export default {
                 "payment-method"
             );
 
-        availableLineItems.push(...(validatePromoResponse?.orderPromos ?? []));
+        const newValidatedPromos = validatePromoResponse?.orderPromos ?? [];
+
+        availableLineItems.push(...newValidatedPromos);
         // End of promo logic
 
         const taxedAvailableLineItems = await baseMixin.methods.dispatchStoreActionWithLogging(
@@ -201,6 +204,15 @@ export default {
             availableLineItems,
             lineItemsFromStore
         );
+        // Add items that were not in the store yet but added via query string promo validation
+        lineItems.promos = lineItems.promos ?? [];
+        lineItems.promos.push(...newValidatedPromos);
+        const vapsToAddToCart = getVapsThatNeedToBeAddedToSatisfyPromos(
+            newValidatedPromos,
+            availableLineItems,
+            lineItems
+        );
+        lineItems.vaps.push(...vapsToAddToCart);
 
         // Call the "next" function to complete the transition to this page.
         next((vm) => {
@@ -412,11 +424,35 @@ export default {
         shouldDisplayPiaAlert() {
             return this.$route.params[this.routerParams.DISPLAY_PIA_ALERT];
         },
+        // Necessary to make the watcher of lineItems work
+        // JavaScript does not keep a record of the old value, only a reference to it's location in the memory.
+        //  This creates a separate location for oldValue/newValue so they can be compared
+        // See Vue github issue #2164
+        lineItemsCloneForWatcher() {
+            return Object.assign({}, this.lineItems);
+        },
     },
     watch: {
         customCtaCopy(newValue) {
             this.updateFooterButtonText(newValue);
         },
+        lineItemsCloneForWatcher: {
+            handler(newValue, oldValue) {
+                if (
+                    !oldValue ||
+                    oldValue.length == 0 ||
+                    !oldValue.vaps ||
+                    !newValue ||
+                    newValue.length == 0
+                ) {
+                    return;
+                }
+                if (oldValue.vaps.length != newValue.vaps.length) {
+                    this.revalidatePromos();
+                }
+            },
+            deep: true,
+        },
     },
     components: {
         funnelHeader,