Yes, I come from the pre-launch / DTM era...
I have worked on implementation in both the s_code.js stage (basically back when this was still Omniture), and the appMeasurement.js stage (the updated files that started rolling in Visitor ID service, and eventually became a part of DTM and Launch).
I hate to say it, but we have a few old sites still running on old tech too...
So first off... you probably have some direct JS code references you want to look for:
s_code.js OR AppMeasurement.js
you may also have a something like OmniLinkTrack.js (which is file that supports your click functions)
Then in the site, somewhere, you will have code that looks like:
<!--
s.pageName = "home";
s.channel = "home";
s.prop1 = "something";
s.eVar1 = "something else";
/************* DO NOT ALTER ANYTHING BELOW THIS LINE ! **************/
var s_code=s.t();if(s_code)document.write(s_code)//-->
^ this here on your page is what is setting your dimension values, then the "var s_code=s.t()" is what is triggering the beacon.