In case you're interested, here's a schematic I was able to pull off an A-10 website.
http://www.a-10.org/flightmanual/man...?PageID=1%2D60
I tend agree with John - the slats probably condition the air as it comes over the wing and enters the engines. Q: Could the airflow be at a higher rate from the engine suction at the wing roots whereby the slats take advantage of this for added lift benefit? Just a thought!
Ted