[NoDOHC]

It is an easy map.

According to our buddy Bernoulli, Fluid flowing through an orifice (fuel delivered) is proportional to the square root of the differential pressure (should be 43 psi for you). This is fixed as the fuel pressure is biased to the manifold pressure, thus the pressure drop across the injector is always constant.

Thus, you would flow 1.41 Times as much fuel at 43 psi as you would at 21.5 psi.

The map should be very easy to plot.

EDIT:

Whoops! I forgot about a factor that will make the map extremely difficult, you are not measuring differential pressure, you are measuring gauge pressure and absolute pressure in the manifold. This math will be a little more complicated.

If you have a barometric pressure input to the Motec, you can configure a Math channel (I think that a Motec will do this). Set the math channel to Differential_Pressure = Fuel pressure + Barometric pressure - (Manifold pressure (in kPA) * 0.145). If you don't have barometric pressure, call it 14.7 psi and you will be close enough.

Now you can use the above relationship to compute your fueling correction parameters and avoid engine damage (we would all be very sad to hear that you damaged the engine while you were checking the local dyno against Dave's).

Another edit due to random thought while at work:

If your fuel pump would ever run out of capacity, it would be at maximum RPM and maximum boost. I think I explained this earlier, I just got to thinking that my previous post was slightly confusing. If the fuel pressure is dropping before the filter, the fuel pump has to be the weak link. A good way to test this would be to pressurize the FPR with a bicycle pump or something to 15 psi and let the fuel pump run for a while. If the pressure starts to drop relative to the bike pump (should run 43 psi above pressure from bike pump consistently). This means that your Fuel pump can not make that much pressure, even at 0 flow (the FPR will eventually shut the fuel flow though it off completely as the fuel pressure is dropping). If the fuel pump can maintain the pressure, The next calculation that you need to make is the maximum flow that you achieved through your injectors (which should be straight forward if you know the injector size).

Next, you will need to get a graduated cylinder and take off the return line from the fuel rail to the fuel tank and feed it into the cylinder. Keeping the bicycle pump at full boost (~15 psi) measure the flow rate that the pump is able to make. Time how long it takes the pump to fill the graduated cylinder 3/4 full. This could take a minute or so, depending on the size of your graduated cylinder, Several liters would be better (I use a 5-gallon pump calibrators bucket).

Armed with this information, you will know conclusively if your pump can indeed supply enough fuel to the engine.

If I were you, I would run the pump for a couple minutes and then retry the flow test (you will need two ball valves to change the FPR return location quickly).