96 fbird sputtering issue

I have a 96 firebird, 3.8l, v6, automatic trans that has a nasty sputtering issue. It starts and idles fine, revs fine in park but when in gear it sputters nasty upon acceleration. From a stop, I have to start out in low1 to get the thing going and manually go through the gears, when I get to a hill I need to drop it into low3 just to get up the hill without sputtering. If I jam the pedal to the floor while at normal speed it sputters horribly then overdrive or whatever it is kicks in and I accelerate normally.
Anyone able to point me in right direction?
Thanks..

Verify fuel pressure is what it should be.