Hey, @Asgeir .
Thanks for confirming that you’re using the Pixel Helper.
If the pixel is not in your theme’s code, then it really sounds like it’s related to one of these apps; this situation is quite common and oftentimes, merchants will still have these apps installed, even though they aren’t actively using them. Although you have not used Kit or Facebook Marketing, do you have either of these apps installed? You can confirm by heading into Apps in your Admin. Merely having the Facebook Marketing app installed, for example, will automatically add another pixel to your store. This can only be removed by completely uninstalling the app. You can learn more about how Facebook pixels are added through the Facebook Marketing app here.
Please let me know if either app is installed in your store!