fuel drops very bad

I have a problem during tuning a s52 project wiling to achieve 1000 whp…. The ecu is link 4gx and an motor sport harness with a full fuel system from nuke two fuel pumps walbro the problem is that when the car starts to go into boost the fuel pressure drops very badly how to be sure that it is not a wiring problem now its about 500 whp

What is your injector duty cycle doing at that point?

Do you have a manifold pressure referenced fuel pressure regulator?

A volt meter connected to the fuel pump would confirm if you have a wiring issue or not.

There are at least four issues you haven't given information on, that need to be checked and confirmed - I assume you have confirmed the lines are properly connected to the rail and

a/ Nuke have a wide range of dual pump fuuel systems - which is the one you're using?

b/ what model(s) "Walbro" pumps are they - https://walbrofuelpumps.com/walbro-gsl-series-universal-inline-fuel-pumps - they make a range of capacities., and are they genuine - poor quality counterfeits are a BIG problem - https://walbrofuelpumps.com/fake-walbro-fuel-pumps - and your location may make it easier for crooks to sell you a fake?

If they don't have the basic capacity, you will never support yout target power, which leads on to

c/ the voltage ACROSS the pump(s), voltage drops not just to the pump but on the ground/earth will kill the potential. Full voltage is critical for achieving the flow against the total pressure head of the rails at full boost, AND to maintain the suction head to draw the fuel from the tank, through the pre-filter and sock (if fitted) - https://walbrofuelpumps.com/universal-in-tank-fuel-pumps.html - scroll down for the illustrative graphs.

With a single pump, up-sizing the wiring will usually suffice, but as you're using a dual pump setup you have a couple of choices - i/ use the ECU "pump" power/ground to switch (a) high amperage relay(s) that have (a) bigger gauge, fused power supply to the pump(s) that provided close to battery voltage across the pump(s), or ii/ have one pump switched directly from the ECU, with the second's relay switched through a manifold or rail pressure switch, or the throttle, to only come on when demand is approaching the limit of the single. I'd suggest the latter as it puts less stress on the alternator, less stress on the pumps, and has a reduced heating affect on the fuel.

However, if there is still a problem after the above, it may be time to look at

d/ the actual fuel lines capacities and possible restrictions/bottlenecks. In this case you aren't getting the fuel to the fuel rail that you need, which means, if a & b, above, check out you are either not getting the fuel to the pumps, and/or you are not getting the fuel from the pumps to the rail.

If you're using socks, it/they may be partially blocked by debris and/or placement in the tank, and/or not be large enough to allow enough fuel through. Depending on the pick-up design, the suction side lines may be too small and/or the fittings used may be excessively restrictive - it's not uncommon for the bores to be MUCH smaller than the hoses, which is why it's worth using special large bore fittlings - personally, I'd suggest going a size or three up from the pressure side for the suction.

If you're using a pre-pump filter (good idea), it may be partially blocked and/or be too restrictive - opinions differ, but my main concern would be having it large enough to minimise pressure drop across it, and being coarse enough to allow little restriction while catching the bigger particles that could cause pump wear and damage.

Assuming the suction side is up to par, you may still be looking at restrictive hoses, fitting, and filter(s) between the pumps and the rail. This is usually a problem when the upgraded pump(s) are used with the OEM lines that were sized for a fraction of the new power level.

If you go through those, I expect you will find you have no more problems with the fuel side - oh, forgot, if you decide to run the pumps full time, you may find you have excessively high rail pressures at low load/idle - if so, it's because the regulator and/or return lines can't flow enough fuel back to the tank - it's more commonly down to the pressure regulator - as with the pumps, it's possible you've been sold a fake, but the manufacturers often have guides to tell the genuine from the fake.

thank you all there was a voltage drop and I solve that problem by using thicker wires and the fuel filter was clogged now the car is doing