What do you have for a tank pickup? You have any tap points where you can monitor pressure? One way to do that which I like, LOL, because I used to do HVAC/R service, is to use refrigeration Schrader valves. I use an old manifold with a different, lower pressure gauge on one side, and the (blue) low side gauge if I need higher pressure for EFI. I use an old set of hoses, so they are not mixed with my refrigerant gauge sets
Another way you can do that for temporary/ troubleshooting is to find/ buy a couple of pressure/ vacuum senders in the proper ranges. You don't need matching gauges, just find out the resistance vs pressure output of the sender. With a chart, you can justify ohms readings to pressure
Does the Sniper electrically modulate the pump? Or just "relay" activate it? Maybe it's losing power from the EFI?