i have a u13 det that i will be installing into a b15 and want to know what would be an ideal turbo to make around 350-400hp on a stock block? just to say

A t4million is the best but it wont spool untill 7million rpms.

Now for real a goal of 350-400 is great but to make that power and do it right your going to spend a ton a cash. Do yourself a favor and just get a t28 or disco spud, 50lbs inj., z32 maf and a good tune/ecu and it will blow your mind how fast the car can be. Keep in mind 280-300hp for 4k rpms(power band) will own 350hp for 2-2.5k rpms. Its all about making power sooner and holding on to it.