I have a hesitation when I take off, I play with gas pedal to Pickup speed

I have replaced the timing belt, water pump, other belt, only because I recently purchased the truck, I have a 4cly, 5-speed, air/heat. The egr valve was sticking so I boiled it now its fine. I also have an issue with my wipers to, they come on spray water, then go off sometimes, im not sure if the clutch is sliping or if its somewhere else. Had parts store hook up computer to it nothing. Please help me.