Help!! Knocking noise

[Stang35]

When i climb rpm's, right around 3000 or so, i can hear fast pace knocking noise, as soon as i let off it stops, and in 5th gear i cannot hear it at all, my mods are listed in the sig(the top one).....What could this be, i changed the pulleys out yesterday on it.

 

[Stang35]

Anybody??

 

[1LowGT]

want to hear something crazy,i asked ford about what sounded exactly like valvetrain noise and asked them is it common and his response was take the belt off,spray pulleys with brake clean and install a new gatorback belt,i thought he was nuts and stupid but i did so and it fixed the problem,my car has 40,000 miles on it