Yes, I experienced the same problem when I was trying to start my 180g in cold weather on 100% diesel fuel. To try and get the ecu to read ignition, I raised the pump value and then I would get flames. So I did what you did and I lowered the preheat fuel, but that's the wrong way to go about it. Preheat fuel is the duty cycle of the main fuel port (injectors) during the preheat phase, while pump power affects both ports.
So if you are getting a slow preheat, odds are your preheat fuel is too low.
Without seeing at least a video of the start, though, these are just pure guesses, so take them with a grain of salt. I am just warning you not to make the same mistake I did and do it reversed
GL fixing your starts!