I have a '00 Legacy B4 Twin Turbo K&N Panel Filter

When I start it up usually when the outside temp is 10degrees or lower and set off driving if I stop at a junction it will stall and then struggle to start again straight away if I leave it 30secs it is ok but I get a wiff of fuel

If it is quite a warm day it is ok

Once warm no problems

I have connected up the Laptop using Ecu Explorer and the temp increases as you would imagine so I doubt it is the coolant temp sensor

I have swapped MAF sensors with my other B4 that is ok and it was no different. I unplugged the MAF and it stalled so that seems ok.

Also there are no fault codes on the ECU