If the end of the linkage that is touching the tank is spare, just cut it off. Or try to reposition the hex nuts in such a fashion that at full throw, they don't touch the tank.

Alternatively, check the throttle limiter on your transmitter. If you give it full throttle, while looking down the carb hole, it should only pull it out far enough to ensure a fully opened carb/throttle hole. Any more and you may burn the throttle servo out prematurely as the signal it's being sent is trying to push the servo further than is physically possible.

That movement you see in the tank is there for a reason, but not to allow the throttle linkage to push it around. It's so that the tank can take the bumps, slams and normal motion and vibration that occur during normal driving / racing.

I can not imagine a car manufacturer spending the time and money on R&D to develop, construct, market and sell ANY type of car that doesn't allow such important functions like throttle / break linkage to move freely and in an un-obstructive fashion.

One more thing you can try if all else fails, use a longer pipe brace to position the pipe a bit further away from the tank.