When I did mine I just installed the reduced diameter EGR stovepipe, it came with the Dorman UIM Kit.
That is supposed to correct the problem enough to stop any coolant leak problems in the UIM Coolant Ports.
You can still block those ports off if you choose to, but I have always felt that if you do so you should remove the Coolant/Water Bypass on the side of the LIM, and hog it out a bit so the flow is not reduced from blocking the ports.
Of course many may see this as just being anal, and it probably is, but I have always believed in going that extra mile to be sure my car is running as good as it can be.
With that said, nobody has mentioned any problems when blocking the ports and not hogging out the area I mentioned, so if you just block the ports you should be fine.
And IMO if you just replace the EGR Stove Pipe with the reduced diameter one, then you should be fine if not blocking off those UIM Coolant Ports.
Note: I went with a new redesigned UIM, if I had went with the old one I may have considered plugging the ports, I am confident my repair will last me for the rest of the cars lifetime though.

This is a post to summarize all that was done on this UIM and LIM project, and as you can tell per dates shown, the weekend project got stretched over the summer into a lazy project timed about vacation opportunities. Never-the-less, I am finished now and vehicle is running fine.
On taking it apart, I found that the manifold had not burnt thru at the EGR tube, so all my water loss was due to the plugged overflow tank hose (radiator thus venting to atmosphere) due to the Dexcool sludge. I have now replaced the upper and lower intake manifold gaskets, upper intake manifold, PCV value, used metal 'L' water connectors, new water pump, new tensioner, serpentine belt, all water hoses and clamps, thermostat and gaskets, new iridium plugs and wires, injector o-ring seals. I installed brass plugs in LIM to close off water flow to throttle body. Also thoroughly cleaned the throttle body, TPS, IAC and MAF. Flushed the cooling system very thoroughly of all traces of Dexcool and installed Prestone Extended Life coolant. Then I changed engine oil and filter, and did a drain/add of Valvoline Max Life ATF along with pan cleaning and new AT filter. Will do another drain/fill in a few months when I have more time. Have also installed new high pressure fuel lines (clamp style) as installing new O-rings in the old connectors never completely sealed after three installs -- not sure why.


I think I covered all I did and must say it runs great (of course it was good before). Should be basically set up for the next hundred thousand miles -- now has 84,535 miles. I really appreciate all the tips and advice I obtained in this and other related posts. Thank you ALL.

Just missed the edit time limit. Forgot to include I replaced the valve cover gaskets while I was that deep in the well.

Sounds like you were very thorough, it should run great for some time to come, and intake manifold failure is not a worry, which is a good thing.

The fuel line connectors you mention, is it the part where they connect to the metal fuel rail?
If so those o-rings are known to leak, at least the rear one for sure, they have two o-rings inside of them, and they are a pain to change.
I went with high pressure fuel hose and clamps myself, at least for the line I had leaking.

WilliamE, I tried three times to install new O-rings at the fuel rail and failed each time, so I just gave up and went with clamps and high pressure fuel hoses to get car back in service. At present I am using just one clamp per position, but want to drive the hose on further and double clamp. The hose is so firm I could not get it down over the ridge on the fuel rail far enough to put a clamp below the ridge. Will feel a lot better about it long term after get it repositioned.
I thought long and hard about ordering the Dorman replacement connectors/lines, but could not confirm their 5/16" line would connect to a GM fuel rail - the ordering guide said it would not fit the return side. The 3/8" Dorman was certified for the GM fuel rail. But I needed both -- so I opted for hose and clamps having already spent three days and several packages of O-rings.

Just get some picks like dentist use I think harbor freight has them.
Then you just fish them out.
Dorman sells a pack of fuel line O rings.
I have done this many times with the factory lines

You can get a special brass compression fitting at NAPA that goes from metal to plastic
if the lines are broke.

I would not trust a clamp on this to much chance of a fire.!!

I bought a pick set specifically to try to remove the o-rings, and I was able to remove them, but getting the innermost one back in place was harder than it should have been.
Not too mention it took me ordering several different 0-rings before I finally got the correct 2 o-rings.
The clamp and hose I went with are designed for well beyond the fuel pressure I have going through the hose, so I am not worried for the time being.
Eventually I'll go back to nylon, but for now it is working well.