That fitting is a one shot. Once you take it off it has to be replaced, the gasket on it goes bad, which usually means the whole line has to be replaced, because of how it works. It's threaded at one end, and inside it, there's a c-clip that opens up just enough to let the flange on the line pass through it, then it clamps down, creating a seal. It is almost impossible to replace that fitting. Recommendation would be to take the lines off of it, install the new fittings in the turbo, then snap in the lines to the receiving end.