Hard start when cold fuel under the car.
 

A fuel leak is not a good thing. I would get the bottom of where the leak is. It shouldn't be to hard. You can first check on the drivers side where the hoses connect between the hard lines going to the rear and where the fuel filter sets there as well. If it is not there then you might have to pull the upper intake manifold. to investigate further. Either the lines going to the fuel rails, injectors, or the line connecting under the upper intake manifold.

My issue I used to have was opposite of yours. Cold start were no problem only hot starts were. This is when i used the fuel cut switch.I have one I used for when it is hot and won't start. I would flip the switch and start the car. When the car starts I flip it back to turn fuel pump back on.

Since you have a fuel cut switch. Have you ever tried to start the car with the switch off? You shouldn't need to do the de-flood procedure since you have that I wouldn't think
.

So first thing is to find the fuel leak. You can turn your car to ON then jumper the fuel pump by the passenger tower there. This way you can look for leaks. If the leak is on the drivers side then you might be able to get to the hoses to replace them if bad or fuel filter without pulling anything. If the leak is coming from the passenger area around the UIM then you might have to pull things off and test again so you can see where the leak is coming from.

////I have tried with the cut off switch off, the car will start with the deflood procedure after several tries
So will it not start with just turning the switch off? Not sure you need to do the deflood since you have this in place. I did this all the time when my car was flooded due to hot start issue however.

////1. Inspect and possible replace both fuel rails, not sure if my car have a fuel punsation damper.
So you will clearly see if the leak is coming from here when you do your test.

////2. Send my injectors for cleaning and test.
No need to do this really I wouldn't think.

////3. Replace all the vacuum lines I can.
Always a good idea however you can test these. I bought a smoke machine just for this test lol. I pull the main vacuum hose running along the firewall from the brake booster or whatever that is behind the master brake reservoir. Then I pull my turbo filter and tape a rubber glove on it. This prevents the smoke from coming out. Then I use a little portable air blower to suck the smoke into the hose and look where it is coming from. I have heard people blow cigarette smoke or cigar smoke through as well. There are other ways. I just found it is easy for me to see if I have a leak this way.

////4. Replace the water thermo sensor.
Only replace if not working.

////5. Replace fuel filter
Always good to replace, but not causing your problem more the likely unless fuel is leaking here.

Lots of valuable information on this site and people to help you with anything.

microtech doesnt use the pump test connector, should run the pump all the time with the key on without any additional steps.

if its leaking onto the floor then you will be losing fuel pressure, leaking fuel is also a fire hazard so if you enjoy having your car you should fix it before driving it again.

Was it MUCH colder the two times it didn't wanna start? Is it possible your ECU, with the 850cc injectors and the way it's set up is part of the problem?

Just wanted to throw that in. But DO focus on the fuel leak first. At best, it's a distraction or part of the problem. At worst, well, that's obvious.

the insulator isn't a huge deal, it does help prevent fuel from boiling in the rails on a hot day after you shut the engine off though.

It also affects the alignment of the injectors between the rail and engine. They'll be at a slight angle without it. Try to find a used one locally.

(Kinda like you want the washers behind the water pump on the studs, or the spacer on the alternator bolt)

Leaking injector O-rings can cause a vacuum leak / lean condition FYI, and be your hard to start complaint.