I could not find a data sheet for a model 2650 but here is a link to a 2660-2680 models and notice in the right hand column the output is 4.4 cfm open flow so should be close performance to your 2650.
On these rocking piston compressors that can handle significant pressures it looks like very little cfm loss at 5 psi. At 10 psi it is only about .2 cfm loss.
Thomas 2660-2680 pump performance PDF FYI
