Can my DME/ECU handle it or do I need aftermarket?

Most Stock DME’s Are Typically Okay for upto 5PSI. Some Pre 1995 (OBD I) such as M50 and M50TU Motors have DME’s that cant just be flashed as OBD II (1995 and After), Such as M52 etc.
I have run the stock DME MS41, Stock Pink Top 21.5lb Injectors, Stock Fuel Pump, Stock FPR and everything just reworked all around to ensure its all 100% working or new. Theoretically your Engine knock sensors generally kill most predetonation caused by running lean and if you do run lean, your oxygen sensors will tell the DME to send more fuel through. So the car will in time adapt a bit however word of caution it will likely run rich and the MAF & DME will need a proper tune to utilize true potential and to iron out the minor issues you encounter.