air compressor size????

Cfm, cfm, cfm!

Gallons of storage and PSI mean nothing after you exhaust the tank.

If you are running a tool that uses 8 CFM on a 5 CFM comp.....

Exactly! It's all about CFM, not the tank size. CFM is the cubic feet per minute a tool draws and it it draws 8 cfm at 90 psi and your compresssor is only putting out 5 cfm at 90 psi it'll never ever keep up no matter if you have a tank as big as a freakin semi hooked to it.