when i accelerate my car hesitates then picks up..and when i gun it again it hesitates again..Do anyof u know what is wrong..if i have a cold air intake ypipe,bpipe..it had happen before i put these performance parts before..Do you think is my throttle body i havent cleaned...sparkplugs..my fuel pump is new...or etc? Thanks hope to hear back..

 

Could be a bad coilpack. You can do a search for coils in this area of the org forums for more information on that.

Does it happen only at certain times? (e.g. when car is cold)

 

Cleaning the TB is always good. I hope you replaced the fuel filter when you replaced the fuel pump if you haven't you might want to, and sparks plugs are so cheap and easy they're worth checking @ least