I am in the process of building a flow bench using one of these blowers I found on ebay. It will pull 28" at at least 325 cfm. Mine has a 2hp 3 phase motor which I will run with a VFD to adjust my pressures. I find that the 2hp model will just get over the 325 mark if driven beyond motor ratings. I am going to upgrade to a 3hp and be able to drive it up to 7200 rpms with blower drive ratio at 3-1
This would be better for a larger bench