how much horses can a stock 2.7t handle before it blows up or how much boost thanks.

you're going to be limited on how much hp you can make if you keep the entire engine stock. For example, the heads are going to only be able to flow so much air to support so much hp. If you're talking about just keeping the bottom end stock, it's very tough to put a certain number on it.

There are guys putting out some large hp numbers...like 400whp+ whose cranks/rods/pistons/bearings seem to be holding up alright, but who knows where the limit is going to be.

Where the boost limit is also is not a defined number. I'm sure someone could "blow" an engine on 20psi if other perameters were not safe...but another engine can very safely run 20psi all day long.

Don't think you're going to be able to just throw GT28rs's on a stock engine and it's going to run to the turbos highest potential. Mark at Autospeed has put a lot of time and thought into working on his GT kit.....I'm sure he'll provide more information later.....but that's a lot of air for the stock intake system and valvetrain to be handling...remember, we're still only 2.7 liters no matter the size of the turbos you put on :)