Oh, and i shouldve mentioned Yerba Maté - the guarauna works better with it, but not at 900mgs of gurana - if you take both, the equivalent would be 450/450 - they both contain naturally occuring caffeine (no shakes, no crash in my experience), but STILL caffeine, so same warnings apply.
Yerba M. also has a bunch
of active compounds ONLY FOUND in
Yerba M., so if nothing else has helped with the withdrawal fatigue, this might.