Just so you know OP stock pumos are Siemens K16s. Like Dustin said, if your not maintaining rail then you have a bad pump but a stock pump should keep up just fine with stock injectors.
Its not that its dropping alot but I can tell I'm at the limit of my stock pump with the way I have it tunes with my MCC tunes. I just didn't know if that would stress the injectors to much but I guess that's all in my tuning.