its a Hifonics BXi1608D, its wired down to 2 ohms so the sub will be gettin 1100 watts i have am optima yellow top am 5 farad cap. will this kill my electrical system
No, you should do the big three, BUT you're not exceeding 1200 watts RMS. You will be fine, should upgrade, and a cap does nothing to help lack of power, only a new alternator will.