4k rpm tip in hesitation

I've got an issue with my 05 6 speed that I tried searching for a solution with no luck. When cruising on the highway between 4 and 4.5k rpm(speed limit on my commute is 80-85mph) and I add a small amount of throttle for say a small incline the engine will hesitate and buck slightly.

All the usual suspects have been gone through in the 6 weeks I've owned the car-
New LS coils
New Spark plugs
New Fuel Pump
All intake valve solenoids replaced, new vacuum hoses
All intake valves operate freely
MAF cleaned
All grounds cleaned

Only mod is an AEM intake. Any ideas where to look next?

Thanks

4k rpm tip in hesitation