turbo relocation pipe size

[Paul Baldwin]

I matches my pipe to what was coming off the manifold cant remember what size that was. To keep up gas velocity. Then 2.5 inch off the turbo. Seems to work pretty dam well to be fair.

As said, match it to what you are working with. What's the point in using much bigger pipe to allow the gases to expand on leaving the manifold to then have to be re-compressed when it gets to the turbo?

Or do like silverzx says and use what you have access to, it'll work anyway.