Well with a supercharger fuel pressure/volume is crucial, especially under boost conditions.
Leaning out too much would be a catastrophic event for your engine.
Did the ESS kit include/suggest upgrading the fuel pump anyway?
What is the age of your fuel filter?
Pop the bottom rear seat and see if the soundproofing on the passenger side has ever been cut. If not, your pump is original.
OEM pump is only about $120 from bmaparts.com.