Hi all

I have a MTA4 S28, which I bought about a year ago and haven’t used it for about 5 months now, but just the other day I decided to pull it out the box and give it a drive. All was well but after about two tanks of fuel the engine started sounding funny. When I pushed the car to full throttle and released for breaking, it continued to make a high pitch noise as if the engine was over reving, but than gradually subsided back to normal. Is this normal, or does it mean the bearings are about to pack up?

Thanks