i had the alternator and battery tested. sometimes its when i rev over 5000rpms and sometimes when i rev over 4500 rpms. also when it turns on all of the lights get brighter. so im thinking its a ground but i cant find which one it is.
Sounds like your alternator belt is slipping at high rpms. Tighten the belt.
yep your belt is slipping
its either loose or worn, check and fix as needed 
Always a good idea to check grounds anyway. Try searching, :hump: as there is a ton of threads, specially in the Electrical Forum.
i checked the belt and its still like new i think my brother in law said he replaced it last year or the year before that, my sister used to own the car. the belt is also still tight.
Sooooo, the brushes inside the alternator might be a lot worn out, ergo, the brushes aren’t being held down at higher rpms. Also, the alternator might not like higher rpms, like the bearings are failing or the regulator is pushing back to much load at those rpms. Also crap belts won’t last a year or two if pushed around alot or if they’re shiny, then they’re coated with crap. Whats to lose, besides a scraped knuckle to change the bloomin’ thing. Eh?:tsk: