more power and speed out of mamba max and 8xl

[Patrick]

Bigger pinion and/or smaller spur.
Use BrianG's calculator to find a spur and pinion combo that puts the final drive ratio somewhere between 14:1 and 16:1. Bigger pinions make the fdr go down. Bigger spurs make the fdr go up. I'm not really sure what different size spurs fit on the new e-maxx.
The lower the fdr the more load you'll be putting on things, so you may need to watch temps a bit more. Good batteries will also become more important when geared for higher speeds.
The type of driving you do will affect what gearing is best for you.