Multimeters can have a habit of 'averaging' voltages and not sampling at a particularly high rate, so that could be throwing off your measurements of the load signal. You'd probably be better off with an oscilliscope when trying to measure it.
There's some suggestion in here that it is based on AMM voltage, RPM and injector constants, but I've never really gotten my hands dirty with LH tuning so I'm just going on tbricks threads generally. Perhaps the RPM signal (pin 1 on EZK) or the AMM voltage isn't right somehow. Supposedly the RPM signal is directly tied to the load signal as well, but that's just others have said so don't know any more than that. Tried MAF cleaner or a good MAF sensor to try and rule that out?
Also I don't think the fans kick in until the engine is quite toasty and I'm also not convinced that connecting the ECU pins for the fans to the relay is going to do anything for this - doing that simply allows the ECU to ground high/low and switch it on, nothing more AFAIK.
I've had the opposite effect when connecting an earlier LH2.4 563 ECU in when you've got an E-Fan connected, as since the earlier ECU doesn't have the circuitry for fan control, and presumably in that ECU the high-speed fan pin is grounded, it switches the fan on full time, as soon as the battery is connected.
I may just be testing wrong?? (have the multimeter on pin 8 and 20 on EZK. 5 and 29 on ECU)
It should be pin 8 on EZK and pin 25 on ECU (though you did mention that earlier in your post so I'm confused ?). 20 on the EZK should be ground?
I kept adding/deleting parts of this reply as I re-read your initial posts so apologies if this doesn't make sense.