Im considering switching the stock blower pulley on my jgp silverado to a 3.3'' pulley. Other than a tune, is there any other modifications I need to make (fuel pump, blower nose, injectors)?

Any Ideas what kind of rwhp this setup with LT headers would put down?

 

When I had the 3.3" I didn't change my fuel pump or injectors. I would guess with LT's pulley and tune you would be around 380 or so at the rear wheels depending on the tune.