No turbo boost please help

[2005powerstroke]

Hello

It's cold out in illinois, single digits some days, I go start my 05 ford powerstroke let it run for a bit before going and I'm not getting any boost. This is on and off problem after truck gets totally warmed up turbo works fine. Turbo is 1.5 years old. Also I have noticed a oil leak on the left side of block at the rear above 4x4 driveshaft by the head possible. Also the headgaskets are intact and not leaking. As the coolant bottle is not pucking.

Thanks for any advise you can give.

[aclem16]

How do you know it's not boosting?