Help! Low speed at full throttle hpi nitro rs4 evo

[stewmcs]

Hello I wonder if anyone can help. My car is running perfect in everyway. But it has just started to stop changing gear and there is no power at full throttle it will get up to running pace then sounds really ill it's sounds great and goes fine if just plodding along but when you start to give it the beans it just will not accelerate and sounds flooded but it's fine at idle and when braking??????