I have the above truck with a 190 hp engine. When I purchased the truck it didn't come with a tow package so I added the heavy duty trans cooler and engine cooler. I also added the brake kit,etc. I'm pulling a 2004 Tahoe trailer weighing in at 4089 lbs according to the manufacture. I carried only about 10 gals of water, 10 gals of LPG, few clothes and fridge filled. The trailer came with a wdh. According to Toyota manual, truck will pull 6000 lbs. I figured I had about 5000 or so lbs. It pulled good going over the Tejon Pass in California going to Sacramento and never overheated. The needle never moved. The truck seemed to be stuggling at least to me anyway. It took off ok even with the ETC on which kept my RPM's up. Toyota told me I was fine. Should I be thinking of a bigger truck?

I'd say you are on the edge of what that truck can handle. Glad to see you using a WDH, that will make a big difference on controling the trailer. You have an auto tranny right?