Vortech pulley size

[Red one]

Not to sound like a broken record, but you need to get the EFI datalogs before going down any other rabbit holes.

No offense taken, I’m fact I’ve gotten in touch with Scott’s tune guy and am gonna go that route soon. He’s a little backed up now, but I have a few differential things to wrap up, so we are on it. I told him I have the stock pump and 255 walbro but he thinks I could be just loosing in tank pressure and the walbro can’t pump what it’s not getting. Anyway I for sure think digging into the tune is much needed. All that said I think I want to upgrade the In take pump with the ones mentioned on here. I think it’s the quantum 340lph, is that correct?

 

[Red one]

On the regulator you key on the ignition (engine off) and let the pump prime and wait for about 10 seconds, the pressure should stay about steady. If it immediately drops way down when the fuel pump is done it's likely letting fuel through to the return or the vacuum line specifically for stock regulator style.

That being said - while driving the behavior observed appears to be more like your fuel pump is completely off or your gauge loses power. Check the ECU safety features like has been mentioned and don't overlook the inertia switch suggestion by Blurry94. On stuff this old it wouldn't be unheard of for someone before you to have tried to "bypass" or defeat it.

Pressure holds with KOEO. What checks can I do with inertia switch?

 

[Required]

Pressure holds with KOEO. What checks can I do with inertia switch?

Just visually inspect it, look for anything not factory. Passenger side floor kick panel, there is a cutout at the top for your finger to press a button. Just look for non factory wires in that area. Could rule out weird wiring issue. Kick panel is easy to remove on that side too.

 

[Red one]

………UPDATE……

So In the end, my fuel pressure sudden drop was I think my no good rock auto pumps. I installed the quantum 340 pumps and no more loosing pressure. I believe I had the cross flow problem with these as well. I also changed my quick 4 tune to the normal rpm range, which is 5k. I had the 6k. Just gonna tinker with the shift points and learn the Holley system. Thanks for the ideas along the way.