You may run a rising rate fuel pressure regulator at the rating of 12:1. This is generally good. There're also 10:1 and 8:1. It's also called the FMU. What it means is it'll add at any given boost PSI the fuel pressure will be 12 times of that amount plus the stock fuel pressure which maybe at 40 psi. For example, at 6 PSI the fuel pressure added by the FMU will 72 PSI, added to the stock of 40 PSI, totalling 112 PSI of fuel pressure. When using this FMU, you must use a high pressure-high flow fuel pump. Normally a 255 lph is a good choice. A high flow isn't enough, it must also be high pressure to withstand the pressure created by the FMU. If you don't use this pump, the regular pump will get stuck and voila, your engine is doomed.
However, some other members run 7 psi (M90 just like you) with stock fuel system on this stock engine without any problems. I don't know if this is possible or not, and I don't want to risk it.