My 2000 Lexus GS300 makes grinding/rattling type noises when I accelerate.

What is your question?

The noises usually starts a couple minutes after the car is started. At first it was only at low speeds but now it's at higher speeds also. Only happens when i accelerate, but there is also a clunking noise like something is loose when i go over speed bumps or bumpy roads. I took it in to the mechanic and he said it was the control arms, which he replaced, and when that didn't fix it he said it was pinging due to bad gas. I've put 5 tanks of premium gas in and i used an engine cleaner but the problem persists. It's been happening for about 3 months.