NVRL8

So after I had my valve covers and piping for the super charger changed out for the ones that were powder coated I started getting this surging kinda studder like if you had a really warped rotor and was barely riding the brake, and this only happens when i'm at 2000 rpms and lower hardly on the gas, but the rpm is not jumping. I've checked and found no leaks in any lines and everything is connected. Any clues?