D-Rodman, is the intake a stock box or aftermarket? I had this exact same problem when I first started driving my swap. I have a v9 motor/trans with a v8 ecu. I noticed you said you aren't tuned, when I was getting the Maf scaling done the problem was going away. Eventually it went away all together. I have a perrin intake on mine.
I did the same as you, cleaned the iacv to no avail. I put my old one on and the high idle I was getting went away but the dipping idle was still there. Talk your tuner and have him scale the Maf before continuing the tune. Be careful driving around without a tune.
Hope that helps.