If you can’t get enough fuel into the engine then you might consider adding fuel into the air intake. There are a couple of examples of this, LPG is one and methanol is the other. Both will speed up combustion as they burn faster than diesel, but adding them can be problematic. If you do it wrong you’ll break things! The benefit of adding a faster burning fuel to the air intake is that you reduce the smoke and burn more of the diesel injected, however it requires fitting extra stuff and some experimentation to set up properly. This is one of the harder mods to get right. See the article on how to cool the intake gases more effectively for more info on the water/methanol setup.