Safe Boost Levels

I see no fuel upgrades. so you likely are.

What would be a safe setting until fuel upgrades are done? What should my next step be? Injectors? Fuel pump? Engine Management?

I constantly read that 12psi on the T3 is the highest safe number.

BUT, back in the day when I had the T3 and run 12psi, I was still pinging my motor. But then again, I am in CO, high altitude.

I guess I will need to back it down to 12. I have not experienced any detonation since running 14. Still would appreciate advice on the next step

Advice on the next step?
Very hard question to answer because we don't know your power goals or where you are going with your setup.

Sticking to stock turbo and what not?
Get 450-ish injectors, walbro 255 fuel pump, and nistune.

This is a very very very common setup to upgrade your stock components and/or going to a t3/t4 setup.

That's it really. When the current turbo plays out plan to go t3/t4. I was assuming as much concerning injectors and fuel pump. Just wanted confirmation which you so aptly provided. Appreciate it.

I guess my reading comprehension/memory is steadily failing. Appreciate the reminder. Your gray matter probably has 20 years less wear than mine. If I could keep a more stock setup that would be preferable. I'm currently pretty close to the goals for my car.

I ran 14psi on my old 85T setup that was in my 88T. Similar to your setup 1986zxt, but I had a pathfinder plenum and a walbro fuel pump. If I hit 15psi at peak torque it detonated a little then fell to 14psi then stopped.

Boost falling off is more of the stock turbo not being able to sustain higher rpms boost or just the internal wastegate not maintaining target boost.

With a gutted asco plenum Id guess you'd run out of fuel faster, like michaelp. Id get a wideband, then you can see when exactly your Z runs out of fuel. Its always slightly different car to car.

~Alex