I'm developing a game and while working on some performance critical parts, I've kinda been flying blind over the last week.

Chrome profiler used to give me great inspiration as to how to improve the performance but for whatever reason, its kinda become useless at this point. Few days ago I refactored some code and gained a miraculous 2x performance out of seemingly nowhere, today I implemented what I thought would be an optimization(took some insert/delete load off from my b+tree implementation at the expense of some in-class book keeping) but turned out to be the opposite and I lost 80% of the performance I had.... Any of these builds profiled on chrome over 30s tell me that I spent 500ms here and 200ms there but where did the other 29.3s go?

I'm profiling the core simulation loop, it isn't huge, just some 1000 lines. Is there a better alternative to chrome when it comes to profiling JS?