Welcome to the forums, and thanks for making a post to try to help others.
I have seen this product before, but I do not think one should use this product, and think that they do not need to remove the lower intake manifold, if you are addressing issues with the EGR/upper intake manifold, and you still have the old style nylon framed LIM gaskets, then I could not see why you would ignore replacing those while you already have the UIM off, also I have heard of more issues with the LIM Gaskets, than I have of the EGR gasses causing a leak in the UIM, not saying the EGR possibly leaking is not an issue...
That product is a bit pricey, you are only getting a small thing that is the equivalent of JB Weld, the reduced diameter EGR Stove Pipe, and a small steel bushing, for 20.00 more, plus shipping, you can get a brand new UIM, with UIM and Throttle Body gasket, and with that steel busing already installed.
GM Intake Manifold Kit
Still IMO replacing the EGR stove pipe with the reduced diameter one that you get in the Fel-PRO LIM kit is enough to keep the EGR issue from happening.
And for those still worried about it happening due to excess heat, they can always plug the coolant ports that lead into the UIM.
Of course I recommend that any that do this, remove the coolant water bypass on the side of the LIM, and hog it out a bit to help keep the coolant flow rate closer to what it was without the ports blocked.
This may not be totally necessary for most, but IMO if you are going to plug the coolant ports as many do, then this is what I consider the proper way of doing so.
Even if you do not hog out the coolant water bypass area, you still do not make the motor get much hotter, I do not think the flow if reduced that much.
Once those are blocked you would not have worry about that, or the coolant ports passing through the throttle body warping, and or leaking.
You had to live somewhere constantly freezing to really need that coolant flow through the throttle body.