How far can you push a 7MGE on turbo?

[Turbotuner2.3]

I tried doing a search and the results i have come across have not really satisfied the questions I have and was hoping sone of you guys can enlighten me, or steer me in the right direction on where I can find some info.

I have a friend with a 87 Supra NA 7MGE, in which he bought a turbo & intercooler kit for it. He told me he had a T4 on some "Godspeed" header, but the turbo took a crap on him and he bought a bigger turbo that isnt going to work out for him. I'm trying to map another T4 out for him so that he can get his car back together because I am going to be tuning it for him.

Some of the things i'm trying to find out are: How far a stock NA 7MGE can be pushed with a turbo kit bolted on, ie:boost levels (and i know that depends on what turbo we get) I was thinking that he might have the upgrade to a high pressure fuel pump and get a stock Fuel pressure regulator from a stock 7MGTE or an aftermarket AFPR, and also looking for a ECU from a 7MGTE? What are some opinions on this.

He wants to stick with this motor for now, and he does not really want to upgrade anything else major. I think he said something about having ASC to tune it, but I dont know anything about that yet.

A little bit of help or direction would be great!
Thanks,
Bob