After playing a few Railjack missions the boost cost increase feels really bad. It's similar in nature to using Apocs or Cryophons with a bad or no Polar Coil. All you end up doing is trying to manage the bar the entire fight instead of just being able to use it when needed. Apparently this was realized as you significantly reduced the heat build up on those guns. Please do something similar and unnerf the boost costs.
The boost nerfs seem excessive for a game mode that DE was wanting to make feel more arcade like. Instead of being able to throw your railjack around with quick maneuvers you just have to trudge around with a slighly faster base speed. As doubling the already slow base speed isn't going to make up for gutting boost. The avionics changes also feel like a way to reduce the total amount of mods we can run on the ship as several of the tier 2 avionics approach t1 numbers while costing significantly less.