Theres several turbo 4's out today capable of 400+ ft/lbs. The issue is the stock internals handling it, because stock turbos tend to make peak torque down low, typically in the 3000-3500 range.
Didn't realize the stock ST's only put down 7lbs of boost stock. And then adding 17lbs netted a gain of 15hp and 70tq. That little turbo must be out of steam.