2001 F-150 5.4l Lack of Power?

I have a 2001 Ford F-150 SuperCrew Lariat 4x4 with the 5.4l Triton engine. I purchased it at the beginning of August, coming pre-installed with a 6" suspension lift kit on 35" tires with everything else being stock. From the first time I drove it, I could tell that the truck had very little power. I have since replaced my fuel filter, oil filter and oil (full synthetic), cleaned and treated the K&N Hi-Flo air filter, replaced all 8 spark plugs and coil packs, and flushed the transmission and installed a new filter. After doing the plugs and coil packs, I noticed a slight improvement in power. However, it still does not feel satisfactory. Whenever the vehicle is in neutral or park and I attempt to rev it, it bogs down and will then rev. In drive, there is no delay of acceleration. Starting is not always optimal, sometimes taking two or three tries to get it to fire up. When I first bought it, the service engine soon light was on, and an OBD II reader indicated it was PO171 and PO174, banks 1 and 2. Since that time, the codes have been reset, however, AutoZone employees are suggesting that the MAF sensor could be causing the issue. I have cleaned the sensor with the pressurized cleaner. Is there anything else that anyone can recommend to draw more power out of my truck? This will be eventually used for towing 2 boats each weighing approximately 4500 lbs, and occasionally an equipment trailer with a front end loader and zero turn mower, weighing approximately 6500. Power needed!

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