My bike has been waiting in a garage for summer last 5 months. During the winter season I have installed leovince cans and powercommander. Of course I wanted to hear that new sound with those cans and started the engine after having those parts installed. Sound was awesome, but...

When I use neutral gear and open some throttle on, the speed reading rises. When I turn the throttle off, the reading follows the rpms and settle down to 0 kmh. The temperature in the garage is maybe something like +5C if the coldness could cause something like that.

Is it possible that I have made a mistake while installing those parts? I tried to be careful and even read the instructions. The installation was simple. I have no idea what is wrong. Any help appreciated!