O2 sensor/harness question

Hello, first post?just joined. To be totally transparent I do not have HP or even have access to it but I am at wits end. I have the following:

ECM/Harness/Engine out of a 2002 Silverado 2500HD (6.0/4L80) that has the triangle upstream O2 plugs.(rears deleted in tune). Long story short, truck is running like crap, rich, inconsistent idle.
Was tuned by a very well known tuner using a mail in service so I wanted to rule out anything hardware related.

I want to rule out the case grounded/isolated ground issue I have read about on the forums. Does it matter which O2 I use (case or isolated)?I?m having trouble following some of the replies. I ask this because I have the year that could have either?from what I?ve heard. O2s are new GM units.

Thank you for your time.

Call your local dealer. Give them the last 8 of your VIN. They will give you the correct HO2S's.

Case/isolated ground is determined by the harness being used - PCMs and OSes and tune settings are the same for either version.

Thank you both!