Im not sure if you mentioned what kind of lift or size tires you were runnin, but you should try a simple front end alignment. I know that sounds way too simple for as much vibrating that is happening but i had the same problem. I was runnin 33's and when driving on the skinny pedal i felt mi entire truck shake, from the bed to the steering wheel to mi seat, and it was a very violent shaking too. I looked into getting hubcentric rings, but the company i called to order helped me out the most. The guy i talked to said its very common with toyotas that havent been properly aligned to vibrate very badly, esp. lifted ones.

If you do decide to try this, you have to do one thing. Make sure to find a good shop. Your everyday alignment shops probably will not and cannot balance and align a larger tire and ur T with a lift on it, they just dnt really know how. I went to a small, kinda sketchy shop a little off the beaten path, but every person there knew exactly what they were talkin bout, you could just tell. Not only did they give me a very good price, they were much faster than any other place and after i picked it up, The ride was smoother than the day i bought mi truck still on the stock 31's. Good luck and lemme know if this helps!