lights dimming

i have a 99 GT, just put a new battery and alternator in and i am having a dimming problem with the lights??? i tested the battery and alt. and they are fine but the likghts dim drastically and the battery light flickers when driving. i am worried it is going to stall while driving. any input?? :shrug: thanks in advance.:)
 
i would make sure that the connector to the alternator is tight. i had that problem with my 94 V6, the connector wasnt making good contact with the alternator, and the lights would dim because the car was essentially running off the battery, the computer, lights, and radio. i was on a trip cross country so i actually just shoved a piece of wood in there to make it temporarily work.

then my rear end blew out so i got rid of the car and got my GT!