backfiring sux..help!!
 

i have ann 89 vert and i just installed a powerdyne 9lbs kit, as well as an 190 lbs fuel pump, bigger mass air meter, the timming is set at 8 degress, shorty unequal headers, an x-pipe, the motor is stock otherwise. I have been experiencing a backfire when i down shift, and the car blows black smoke sometimes when i shift... please help, i think im running to rich, i need advice
Thanx