[Schulisco]

When there's suddenly too less fuel and preventing cold start this could be caused by several things:
1. WUR is bad
2. Vacuum leak(s)
3. Clogged fuel system
4. Fuelpressure too low due to corrosion in the gas tank / fuel pump / defective fuel pump

How old is the fuel? How long is the car sitting now/before the issue? Old fuel can be a serious issue on starting problems.

A bad TTS does not prevent a successful motor start. OTOH you can give the engine a shot of start spray just before cranking/starting. If it then starts it might be a bad TTS or sth. else like the listed issues.

First of all I recommend to check the control & system pressure before taking another action. You need a CIS pressure gauge to do that. If it's proved that both are correct and in spec next steps have to be made. You can build it by your own or order a ready made.

The procedure of checking the TTS is beside other threads in here:
https://forums.pelicanparts.com/porsche-911-technical-forum/1167812-intermittent-no-start-how-test-4.html

Thomas