For those pulling long trailers long distances you may check into getting one of this:
http://www.transferflow.com/shop/product/0800115964
I just found out about it too late because I just trade my Taco for a 2015 Tundra.
I pull a Jayco 161 OctaneZX Toyhauler, dry weight is around 4,200lbs and I load it with a Polaris RZR 900. For short trips I have no problem but for trips lasting over 2hrs this is not the truck for the job. The reason 150 miles range before refueling.
My Tacoma is a 2012 DCSB 4X4 TRD OffRoad...