DC2TurboTeg00

I'm running a drag turbo kit on a stock B18c, for engine management I'm running a Vafc-2 and a Fmu. I have a fuel filter mounted B&M gauge and a stock fuel pressure regulator. My pressure jumps constantly between 42-46 at idle it ever sits still. Stock fuel pressure for a Gsr is 42 psi but I was wondering if it's suppose to stay at 42 or is it suppose to jump around at idle like that? I swapped out gauges with a friend and it does the same thing so I know it's not the gauge. Any info would be greatly appreciated!!!