HHO generator on a pre EFI diesel

[pinchers]

Hi there,

Im in the process of building my own dry cell generator, im looking to install it into my toyota hilux pickup which is a 2.4 diesel with a mechanical fuel pump, ive read about PWM's for control over the vehicles O2 sensor but how will i control the HHO generator output relative to the fuel injected if there is no electronic way to measure it?

I use the vehicle for 4x4 events and i am looking to swap the engine in the very near future for a 3.0ltr turbo diesel (mechanical fuel pump) so i was wanting to test and prove the system on the 2.4 engine ready for it to be swaped into the larger engine when im ready.

Any help would be great as fuel over here in the UK is at silly prices