i have noticed a 2" crack around the join on the cast part where it and the turbo joins , how much would this affect performance ?, and is it possible to seal the crack, dont really wont to replace whole lot as my turbo only a few months old, or has someone got a old td05 16g laying around and wont to just sell the cast part.

 

If you're talking about the 'ring' cracking on the exhaust housing, where the stainless band attaches it to the core, then yes it can be V'd out and welded up, then dressed back to allow the clamp to be refitted correctly. - I've done this a few times, but it's probably easier to just source a new exhaust housing