Right, I know both of them can be improved through the upgrades in the tech tree. Currently, the dusty plasma is at mk 4 outputting 6 GW and the generator is at mk 2 at 85% efficiency, meaning with this exact setup the maximum value is 6 * 0.85 = 5.1 GW. If they were both at their full potential, the reactor would output 9 GW and the converter would process at 95%, resulting in 8.55 GW. I don't think that's the problem.
I guess the root question here is why the engine is only requesting a third of its maximum draw according to the VAB?
(The new UI changes look good though!)