First thing I would want to do is datalog to see what the pressure is actually doing. If you're actually seeing a dip in pressure when going hard throttle, then you should be able to rule out sensor. Based on when it is happening it sounds like a common HPFP issue though.

This is why every BMW owner should just pony up the 30$ and get a diagnostic cable. Would give you a lot of information prior to posting a thread about it. The 30$ is worth it just for the possibility of not getting any ignorant DB replies from certain people.