I don't know much about Toyotas, but I can tell you from experience that GM trucks will act just like that if there is too much alcohol in the fuel, or if there is water in the fuel.

The water floats/rolls around in the tank and sometimes gets a little sucked into the fuel pickup.

Since all new GM trucks have fuel deadheaded to the fuel rail, the result is a rough run condition that starts and ends with the rearmost cylinders.

This is expremely difficult to diagnose since it is dependant on the tech catching it in the act while in the shop. It's one of those things that is almost impossible to diagnose on the road since you can't obtain a fuel sample while driving 55-65 mph.

About the only reliable way to check [for water] is to remove the fuel tank and take a look inside.

If alcohol is the problem, there are electronic testers for that. The dealer should have one.

How many tanks of fuel have you gone through like this? Have you tried getting your fuel from another station?

One last thing, do you have a K&N air filter installed?

Clay