I own a 2006 touring AWD with 59,800 miles.

Over the past few thousand miles, I have noticed what can best be described as surging when accelerating. I notice it most on a warmer day while using the A/C. I also noticed it the other morning while driving approx 76 MPH, (our highway speed limits are 75) pulling a steep hill. The tranny shifted down to 3rd, I was not running the A/C and it was approx. 60 degrees F out.
The pac hasn't thrown any check engine lights and it is idling fine. The condition isn't getting any worse although; the power and fuel mileage are down a bit.

I replaced the plugs with factory platinum plugs @ 30,000 miles. I recently replaced the pcv valve. I also checked the condition and gap of all of the plugs. They were all the same light tan color. The gap was perfect. I used an ohmeter to check the resistance across the coils however; I was told that the only way to detect a bad coil is while it is under a load.

I have not checked the condition of the fuel tank sock or the fuel pressure.

Does anyone have any suggestions?