poolsmillrods

I just finished a 5.3 swap in my 68 c10. It has a ls1 intake with the stock 5.3 injectors. My prob is it seems to idle great and smooth but if i try to drive it its like it starves for fuel under most of the throttle range except just off idle or if i floor it its like you fliped a switch and it takes off which i have been told is pe mode. Im not getting any codes. Do you think its something in the tune? I had a local lsx shop flash my pcm and told them what i had done. I was thinking mabee its something in the fuel mapping but im not a tuner. Any help would be great.