Hi. I have an 03 reg Nissan Micra 1.0, only purchased a couple of weeks ago. It drives fine up to about 40mph but then becomes noisy, so that after 50mph it is really annoying and it seems to struggle a bit! Not sure if it's just because it's a 1.0 or if there's a problem somewhere. Also, central locking clicks locked then unlocked constantly as you're driving. Any advice greatly appreciated!