Quote Originally Posted by dbltoe View Post
You'll need to find which of the Google Tag Manager IDs belongs with the current site and remove the non-current.

While it probably doesn't affect site performance, Google does not recommend having more than one gtag.
What Google exactly says is:

keep the number of tags [...] as lean as possible

Most browsers will not open more than four to eight HTTP requests to a single domain at a time. If you have a high number of tags on the same domain firing under the same conditions, tags will only fire within this browser limitation.

https://support.google.com/tagmanage...72488?hl=en-GB