I’m unaware of any methods of disabling garbage collection during execution of a specific code fragment (if you know them, please share). You can manually execute only non-incremental major GC runs that take very long time, and if you run them after each player script is over, it can easily make ticks 2 times slower and even more.
Besides, another problem apart from the GC is runtime code optimizations that the V8 executes when analyzing code. They are very dependent on usage patterns that can vary from tick to tick, and various optimizations can behave differently.
As for the API methods relating to CPU controlling – yes, we consider adding them in the future.