2004 Jeep Liberty Engine Miss

I have a 2004 Jeep Liberty with a 3.7 gas motor. It starts, idles and accelerates normally. The problem occurs when the engine is above 2000 rpm and you take your foot off the gas (idle decel). The engine slowly decels and then for a couple seconds, it shudders(shakes) and the rpm rapidly decreases to 600 rpm, then right back to 1700 rpm or so where the IAC is supposed to slowly retard the engine. It does it several times before settling down. If you operate below 2000 rpm, it decels normally. I have replaced the: IAC, TPS, MAP(sensor), CKP(sensor), CAM(sensor) and removed and cleaned the throttle body. The MIL light is not illuminated and have scanned the car with my genisys.
No problems can be found. If you have any suggestions, please advise. Thanks, Don