12psi will push the IAC open. I tested this theory a couple times and When removed thre IAC was opened (pushed back). You have a couple options. I made a sleeve that goes behind the pintle that holds the pintle to its fully closed position. Another method is to put 3 pennies in the IAC hole and push the pintle all the way in.....Now re-install the IAC. This will block off the IAC port as well.