I used the typical "internet-order-online" replacement UIM on the '99, and it has worked out just fine. (it comes with all new gaskets/seals)
I TOTALLY RECOMMEND AGAINST using ANY Part, I don't care who makes it, and still allow the hot EGR tube to come in contact with the UIM. Come on guys, this ain't even any scientific mystery here,,,,, Put a hunk of plastic of the stove, and heat it up for a few years, and see what you get. -I don't care how "high tech" that we immagine the plastic may be,,,,,
It is totally simple: You have to get a barrier, preferably with some air space, between the hot part, and the plastic. The Ken-Co kit does a great job of doing both. And granted anyone with a slightly inventive mind can come up with their own mods that will also work just fine and dandy.
If your original UIM is not totally ruined, then the sleeve and epoxy will fix it.
And yes, I reused the all the original gaskets on the '02 UIM when I put it back together. Since they are red silicone beaded gaskets, they should essentially last forever.
AND, the '02 already had the smaller EGR tube, so I didn't have to mess with that part.
As for the LIM gaskets, that is a little different story. As I have stated before, the blue silicone GM units, with those four little splits in each coolant port look pretty questionable to me, when compared to the red silicone FelPro or Victor units without the splits. (afterall, that was the apparent point of failure on my '99 gaskets, so why wouldn't I expect that replacing them with the identical design part is only "resetting the time-to-failure clock" to last just about as long as the originals.)
Hey, I honestly don't know about the LIM gaskets, but that is certainly my opinion.