Engine Surging at Cold Start & While Towing. Round 2.

I have a 2011 Tundra Limited 4x4 Crew Max with the Flex Fuel 5.7L engine. Anytime the outside temperature is around 45 degrees F, or less, and the truck has sat overnight, when I start the engine and leave home (I have a mile of 25 mph speed limit before I get to a road where I can do 55 mph), when the engine gets to 2000 rpm, it starts surging and bucking and will keep doing this for a quarter mile to a mile, or until I accelerate past about 2700 rpm. The surging and bucking is much worse the colder the outside air temperature. After a quarter mile to a mile, it quits surging and bucking and runs fine.

When towing my camper trailer (5000 to 5500 lbs) in cool to cold weather, when pulling hills, when the engine is in the 2000 to 2800 rpm range, it starts surging again, and without changing gears, the rpms fluctuate up and down about 200 to 300 rpm. This happens at normal engine operating temperature and has nothing to do with how long the engine has been running.

Also, I have NEVER run any E85 fuel in it and it does the same thing whether burning E10 or E0 fuel, 87 Octane or 93 Octane.

Also, the gas mileage is abysmal. I get 17mpg at 50 to 55mph, 12 to 14mpg at 65 to 70 mph, 10.2mpg in city driving, and 6 to 8mpg while towing the camper.

My truck just turned over 117,000 miles and I replaced all four of the O2 and Air/Fuel ratio sensors in the exhaust system this past spring with factory parts. I've also changed the spark plugs, had the transmission fully flushed and fluid replaced at the dealer, antifreeze fully flushed and replaced at the dealer, etc., etc., etc. I keep up with all the recommenced maintenance. I've also cleaned the MAF sensor and throttle body with the proper aerosol cleaner.

Of course, the two dealers I've been to with these problems were absolutely zero help and found nothing when they ran a scan through the OBD port.

I would greatly appreciate any help or insight that you can give me with these problems. This is becoming such a problem that I am beginning to consider getting rid of this Tundra and going back to Ford F-250 diesels (said while gagging).