Blasting Cabinet Metering Valve

I think I might have found the trouble. The blasting gun has a very small amount of suction going on, but I don't know how to remedy that. I did just get a new set of tips. There were small, medium and large. I got the small thinking that would conserve more air. Could that be affecting the suction to the pickup hose? Yall give me some help here. I'm bout pissed off with all this.