Tubular manifold
 

I have finally come to the fact that I can build a good one with saving alot of money, so I was wondering what outer diameter you usually use for a 2 liter in the piping.

Well ID is what matters, not OD. But the displacement is only one of the contributing factors to the header dimensions. What size turbo? How much power (Realistically) are you looking for? What's you peak torque RPM goal?

Well I am doing another Holset build, Hx35 7blade, its a T3 divided stock 12cm exhaust, realistically looking to push 500-550 whp with 30ish psi, peak rpm being 8500 to 9000

unless your going with a built engine just throw together a nog log man way easier to make and you can get log manifold kits for like $60

Yea, I actually used a DNP on my last car, but thats gone and I think it would be a little better and unique if I were to go at a manifold on my own, and yes, the car will be fully built, and I am looking to make that power on pump gas and meth, but I will have a second tune for race gas but I do not want to post aspirating numbers on that just this soon. Those log mani's are really good for small power setups though, I am just new to the whole building your own manifold thing and I cannot find any info on the size of pipe to use.

Oh and this is for my dsm hah.

use 1.5" I.D. pipe