2005 Fiat Stilo Car feels like it loses power when driving

2005 Fiat Stilo Manual 42000 miles

Hi, I have a problem with my car, whilst driving it loses power, problem is intermittent, twice it has stalled after I have driven up a steep hill, the car struggles to stay on, it chugs a little then stops. It takes about 5 mins to get started again. I press the accelarator but there is no power at all at this point. While in motion I feel the car struggling sometimes as if it loses power. Please help as I am at the end of my tether. Recently I had a hole in my turbo intercooler pipe worn away by the engine covering, which was accompanied by a whooshing noise. That has now been fixed, no whooshing but still pulling as I drive.