When the 200gph systems were first released, low speed was 50%. We've since changed that to 40%. I don't remember the exact date off hand, but it was quite a while ago. If the truck is streetable, low speed is plenty of fuel. The 100gph kits are single speed. Something to keep in mind is that the 100gph and 200gph ratings are not only at pressure (not free flow) but usually a shade on the modest side.
The 100gph systems are good for about 500hp and the 200gph systems are good for nearly 2000hp with the add-on regulator.
If you use the Fuelab install kit, the harness is configured such that it (the 200gph system) will be in reduced speed mode constantly.
If the center (yellow) terminal is grounded, the pump will be in reduced speed mode. When you remove that ground, it will be in full speed mode. Again, if the truck is remotely streetable, low speed is more than enough fuel. There might be an exception, but I've yet to hear about it. You can also send a PWM signal to that center terminal and have variable speed out of the pump, but it's very rare to see a diesel customer do that. That's a feature that I see used very often in the gas market, where aftermarket ECU's (which have PWM output capability) are relatively common in a drag/track car.
Depending on the amount of fuel your truck needs/the mods you've done, the injector pump may be able to pull enough fuel through a pump that is not running. There's obviously a limit as to how much the injector pump can pull through though- that would be my assumption as to why some trucks will still run while others will not. The pump is flow through, but there's a limit as to how much can actually be pulled through it by an injector pump.
We were able to lower our prices some. However, we are still a bit more than the competitors. There's really no way around that. A brushless motor and the driver/controller cost much more to manufacture than a standard brushed motor. We'll never be able to match them in price, but we will surpass them in performance and reliability.
There was some mention about the install kits as well. It is true, you do need to purchase an install kit or DIY. There's a couple of reasons for that. Some people prefer to DIY rather than buy a kit. Additionally, we give you the option of a full install kit or a switch-out kit. The switch-out kit is for those that have already upgraded to larger lines and fittings from a previous install of a performance lift pump. That kit just provides the fittings you need, while allowing you to re-use a lot of the old install parts.
If anyone has any tech related questions, feel free to contact me. I am not here for sales support though- please keep it tech, install, or troubleshooting related.