i see all these turbo and non/turbo Exhaust manifolds and alot of people seem
to be using more smaller pieces and welding them to the collector or from the flange
is there a reason for this or could you just have pipes bent to spec and weld them
is doing it in alot of smaller pieces stronger than prebent piping and welding it that way?

 

That is one long *** sentence. Try using periods like you were taught in school.

To attempt to answer this I'll just say that using the multiple pieces is the result of readily available sch. 10 and sch. 40 prebent pieces. You can buy the bends and straight pieces direct online from ace stainless or Mcmastercarr then just piece your manifold together.

Using 16 ga tubing that is prebent is obviously cleaner looking, but the tooling required is more expensive. In the end sch. 10 and 40 manifolds are extremely strong. Also, don't think that more welds are an indicator of weakness. If the welds have full penetration they are stronger than the metal that surrounds them.

There is alot to this. Do some research on this website and your questions will be answered.