hestitation in first and second gear

Hello everyone this is my first integra and I don’t know what is going on. When the car gets up to normal operating temp. and, I go to take off from a light I put my foot on the gas, the car the car seems to rev but it doesn’t move until I get to about 4000rpm then it just takes off. The same thing will happen if I slow down in second but not stop and, it will also happen in third sometimes but very rarely. I also noticed that when the car starts hesitating it will back fire almost every time I shitch gears. Just to let everyone know I have aready changed the fuel filter, plugs, cap,rotor, wires, timing belt, waterpump and a new clutch. (I just bought the car three weeks ago). Any suggestions would be very appreciated. By the way I need to get this problem fixed because I’m tired of getting smoked by stock Neons. THANKS :sick: