88 T-bird Idle Problem

I have a 88 t-bird with a 5.0 HO motor and was having a problem with the car dying at lights or stop signs,etc. so i changed the plugs to start with and now it's worse. it had split fire plugs and i installed ac's. any ideas?

the car is an 88 but the motor i am not sure of when asking for the plugs and such at say autozone should i tell the motor type 5.0 ho cause the man who helped me with the plugs said it shouldn't matter about the plug gaps on the 302's