1994 Ford Tempo alternator

I know Ive asked a couple of questions about my car and it was about the stalling at a stop but I had someone look at it and the motor does not belong in this car the engine is a ford taurus S H O and when they looked at the engine they were suprised and I didnt have a clue to why they were that way I found out the problem and it was a combination of MAFsensor and the 2 of the 02 sensors top and bottom my car is very fast now I kept up with a mustang 5.0 but I have a nother problem I put a massive sound system in it and that consist of 4 12'' high powered subs and 3 amps 1 is 3400watts at 1ohm stable(subs only) and 2 1000watt at 4ohm rear (mids and highs only) and 3 a 600 watt at 4ohm front (mids and highs) orginaly the car had 4 factory speakers now I have 10 not including tweeters. And I have a second battery in the trunk but my lights and everything flicker to the bass and the amps are reading 9.2 volts at 189 dbs could my alternator be going out caus my amps are suppose to read 12volts when my aps are on durring music play they desplay dbs and voltage thanks