2002 Ford Expedition Surging

Replaced the PCV valve and checked for vacuum leaks. Engine sounds quiet but for the AC compressor kicking on. Unusually quiet actually. Took it down the road and the same problem is still there. I did notice when you are sitting in park then give it some gas and bring the rpm's up to around 1500 then quickly let off the accelerator, the rpm's drop low and the engine starts acting like it wants to shut off before picking back up again. I checked the throttle body to see if it was sticky in any way but it releases and bounces back very well. Also, the check engine light has never been on but I'm tempted to take it down to the parts store to have it tested anyway just in case I can get lucky.

I was a little worried about the valve clearance problem so I went to the nearest auto part store and purchased fuel system cleaner (x6). Followed the instructions and the hesitation has stopped along with the rpm idle being erratic.