HELP!! 3.6 - 3.8 upgrade Page load Speed issues

Hey everyone, this is my first post. I looked through and could not find something similar, so I am creating a new topic here.

We have about 20 clients on 3.6 or 3.8. We have been upgrading clients from 3.6 to 3.8 for a while and have not had any issues. Yesterday, we upgraded our largest, most trafficked site from 3.6 to 3.8 and in doing so the page speed dropped from around 6 seconds to near 30 seconds.

Hardware:
Web server:
Xeon 8 core
16 gb ram
Server 2012 R2

db server
SQL 2016
Xeon 4 core
16 gb ram
server 2012 R2

Installed plugins:
DiscountRequirement.HadSpentAmount
DiscountRequirement.HasAllProducts
DiscountRequirement.HasOneProduct
DiscountRequirement.MustBeAssignedToCustomerRole
CurrencyExchange.MoneyConverter
ExternalAuth.Facebook
Misc.FacebookShop
Payments.CheckMoneyOrder
Payments.Manual
Payments.PayPalDirect
Payments.AuthorizeNet
Payments.PayPalStandard
Payments.PurchaseOrder
PromotionFeed.Froogle
Shipping.AustraliaPost
Shipping.CanadaPost
Shipping.FedEx
Shipping.FixedRate
Shipping.ByWeight
Shipping.UPS
Shipping.USPS
Mobile.SMS.Verizon
Tax.FixedRate
Tax.CountryStateZip
Widgets.GoogleAnalytics
Widgets.NivoSlider
SevenSpikes.Core
SevenSpikes.Nop.Plugins.ProductRibbons
SevenSpikes.Nop.Plugins.SaleOfTheDay
SevenSpikes.Theme.Brooklyn
SevenSpikes.Nop.Plugins.HtmlWidgets
SevenSpikes.Nop.Plugins.StoreLocator
SevenSpikes.Nop.Plugins.NewsletterSubscribe
SevenSpikes.Nop.Plugins.SocialFeed
SevenSpikes.Nop.Plugins.AjaxCart
SevenSpikes.Nop.Plugins.AnywhereSliders
SevenSpikes.Nop.Plugins.FacebookShop
SevenSpikes.Nop.Plugins.JCarousel
SevenSpikes.Nop.Plugins.MegaMenu
SevenSpikes.Nop.Plugins.QuickView
SevenSpikes.Nop.Plugins.RichBlog
SevenSpikes.Nop.Plugins.Attachments
EmailTracking.Listrak
Widgets.GAEnhanced
SevenSpikes.Nop.Plugins.SmartSEO
Widgets.FacebookPixel
Widgets.AllInOne
BrainStation.ProductVideo
SevenSpikes.Nop.Plugins.NopQuickTabs
SevenSpikes.Nop.Plugins.SmartProductCollections
SevenSpikes.Nop.Plugins.CategoriesHeaderMenu
SevenSpikes.Nop.Plugins.InstantSearch
SevenSpikes.Nop.Plugins.AjaxFilters
SevenSpikes.Nop.Plugins.CloudZoom
SuperNop.Plugin.Misc.ShopByLook
SevenSpikes.Nop.Plugins.PrevNextProduct
Pickup.PickupInStore


Processor is around 90% steady and page load is around 30 seconds.

Does any one have any recommendations or had a similar experience?

have you enabled the mini profiler and check that where it taking more times ??

have you try to use sql profiles to check which query take more times ??

did you applied the performance improvement tips etc ?? like configured the performance related setting etc ??

its hard to give you the reason directly without checking in details.

i think i can help you with that but i need more details

Thanks for the reply Vipul!

We were able to band-aid the situation by turning off the Mega Menu after we discovered that it was consuming significant resources when trying to get catalog data.

We have not yet turned on minification and other settings yet, because we wanted to get to the same state as we were on 36 in order to have a baseline for the 38 improvements. How do I utilize the profiling that you mentioned?

Please check few links

https://www.nopcommerce.com/common-tips-settings-recommendations-to-optimize-performance-in-nopcommerce

https://www.nopcommerce.com/boards/t/46392/performance-optimization-for-38.aspx

https://www.nop-templates.com/performance-optimizations-in-nopcommerce-33

please for checking in detail enable the miniprofiler from advance settings and check which is taking more time

There are too many plugins installed.

Nop cant handle a large plugin quantity very well. install only necessary plugins and delete all unused, I mean, delete by erasing the folder, only uninstalling doesnt help. Nop loads all dll even plugins that are not installed.