Rebuilt SR20DET Turbo Selection

[Quiche2192]

So I've completely rebuilt my SR but I'm having trouble deciding which turbo to get because of a couple reasons I'll explain. Let me share the setup:

- 400 WHP goal
- 9:1 compression ratio
- 93 Octane pump gas
- Stock intake and exhaust manifolds
- Stock ECU with RS Enthalpy tune

Here's the thing that's holding me back:

- I really want to maintain the stock exhaust manifold. Don't want to deal with cracking manifolds, and I like the subdued bottom mount.

- I've been looking at the G25, and the GTX2867R Gen II. Mainly looking at the GTX2871, because they make a drop in for the SR.

- I keep hearing the G25 is worth it, so I looked and they only offer a T25 version of it with a .49 A/R. Is that too small of an A/R and will it cause back pressure? Where can I find more detailed technical info about this?

- With the smaller A/R, if back pressure is no issue, would it make sense to go with a G25-660, instead of the 550?

https://imgur.com/IfplzM2