With alky and 50lb injectors, you should be able to run as much boost as those turbos can take. I ran 25lbs boost on the 6152 turbo and only needed 80% injector with the alky. With alky the chip burner will take out some injector as the alky replaces some of the fuel.
Directscan is good at showing injector duty cyle if you don't really know how much injector you have. Or you can ask whomever made you chip how much injector it is programmed for at a given rpm at WOT. With adjustable chips you can program the amount of injector until you get it right. You need timeslips and EGT or wideband #s to get the right settings along with some trial and error. Each car is different though and the chip will be programmed as the typical injector settings for people with a similar combo.
Old way to adjust was with fuel pressure but better is through an adjustable chip (some even have real time wideband feedback to the chip).
If you already have a chip for the car and its burned for 20lbs boost, you shouldn't go over 20lbs of boost unless you can adjust the fuel/injector in the chip or you'll run lean. If you upgrade the turbo, running 20lbs on a bigger turbo may mean you'll run lean also. A newer adjustable chip like the one from Turbotweak lets you adjust the fuel/injector in the chip over a wide range so could use the same chip for a stock turbo at 20lbs or for a 6131 turbo at 25lbs as long as you adjust it correctly and have good feedback through your gauges to let you know when you've got the settings dialed in.
So, maximum boost is relative. You could probably get 25-27lbs boost out of those turbos but it might depend on how good your stretch IC is.
With your combo, less than mid 11s and you'd be leaving something on the table. I ran my 11.4 on a tired engine with a stock IC, stock MAF and an inefficient unlocked converter. But the tune was good and I was getting consistent mid 1.5 60s off the footbrake. I ran 11.6 on a TE44 for comparison, everything else being the same.
