There seems to be a discoloration of the fuel pump cover, which is usually caused by installing the crankcase cover (with the fuel pump bolted to it) and not getting the tongue of the pump completely into the groove in the flywheel bolt. Or, not running a gasket behind it, which in some cases can allow the tongue to bottom out. This pushes the gear/shaft combo of the pump against the pump cover and heats it up until it discolors and potentially warps. Once it is warped, the pump can't maintain prime and becomes ineffective. The fuel pump is the most critical component of these systems these days because nobody I know has been able to find a replacement for it and MRD isn't fabricating the pump covers any longer.
Throttle response is as advertised, but you do need to know or learn about what you are doing because if you set it up too lean, it will run great right up until the pistons burn up.
