Daniel Joseph Bragenzer Bond

hi everyone. I recently installed some new subs and amp. 2-15" RE Audio XXX and a MA Audio HK-4000D. Heres the problem.Amp is going into protection mode when i open it up all the way due to (as far as I can tell) voltage dropping.It holds 13.3v most of the time but certain tones drop it below 12v shutting it down. Ive done the Big 3. Got 3 Kinetik batteries .2 HC800's under the hood and a HC3800 in the trunk. currently running stock alternator 120 amp. there is no available H.O. alternator made for my car(2002 hyundia XG350L) looking into having my stock alt beefed up. there is 1\0 gauge rockford fosgate power cable throughout. Also something weird,when the trunk is open it will shut down at half volume.trunk closed almost never shuts down... Any Ideas?? Thanks