Bigger injectors with a supercharger?
 

I will be running 9 pounds of boost into my stock 5.0 engine. My mustang shop said bigger injectors would be a good idea. They said it wouldn't give me any HP gains, but would be an "insurance" that my engine will always run rich and have plenty of fuel. He says if it runs lean at all it could blow a piston. What do you guys think, should I get the bigger injectors? Do I need them? Do you guys run them, and if so, at what point did you decide you needed them? Thanks in advance:)

Get the injectors. Your shop was right, they are good insurance. Not enough injector = not enough fuel = boat anchor if you know what I mean. 9 lbs on a stock motor, get 30's minimum and a 255 in-tank fuel pump(GSS340).

Running 9psi with 30's is not going to be a problem. The 30's will allow you to tune WITHOUT the FMU which is a huge plus. Also, I'll second the opinion of a big fuel pump (Walbro GSS305 or GSS340 will both work)