Different cars react differently to the box. The reason people are telling you to get the CANtool from BMS is that you can set it to automatically delete nuisance codes (which are very likely causing your SES light). This way, if the engine light comes on, you know it is something real or your car is letting you know that it doesnt like the JBD at that level. currently, it is simply your car telling you "you are manipulating my rail pressure" which you already knew.
Personally, I don't get an SES light with JBD (sans cantool) unless I am at >90% and I floor it while it is cold (which I don't do), but everybody's car is different. Think of your car like an individual. Some people will put up with being manipulated, some even take pleasure in it, but most will either remain completely oblivious or really kick back when aware of what's going on.
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