I would not bother with wiring into the ECU. I just need a stand alone with meter or gauge and o2 sensor. And like you said, test, get it right and remove it. I would like to pass smog the first time.. That's one thing that sells me on the LCI header over the DT unit. Too many complaints about the required smog fixtures beat to help. I also read that the DT headers are now made in Mexico at the Petronix exhaust factory. I will call DT tomorrow and ask a bunch of questions.
I like your thinking process. You are analyzing, for yourself, the aspects of your needs.
It's interesting that over the years most of us have read and heard various "opinions" and "experiences" on just about everything related to our hobby.
Unfortunately there is a large percentage of bravo sierra on the internet, so you have to be a detective and open-minded to the difference between fake news and the facts and truth.
BUT.... experiences differ, so one man's euphoric rave may be another man's dysphoric rant.
Regarding the header - I would go by my gut, and it seems you are really leaning towards the LCE header.
The LCE header is very high quality, and those who have installed one have raved about it.
Where something is manufactured is a whole other topic for discussion, and there are many examples of what it means to us as a consumer.
For example, Chevy has a plant in China... Chevy is a highly rated vehicle. Most of Toyota's are manufactured here in the USA - also highly rated vehicle.
So, if the quality and fit of the header are your top concern, I'd go with an LCE.
I appreciate you posting your thoughts and experiences.
I don't think you can go wrong with an LCE header.