Being seen is a universal problem with motorcycle, in the US as well as abroad. Here we'll over 70% of car v motorcycle accidents happen well within the rider (and driver) field of view, rarely from directly behind (where your exhaust is pointing).
HiViz gear, auxiliary lighting, lane position & presentation, etc. as well as driving defensively/with a high degree of awareness (for instance use the SEE strategy from MSF) can all increase your chances of being seen.
Most cars are now built to eliminate road noise, provide a more rich audio experience from within the vehicle and attenuate external noise so being visible, especially with all of the on car distractions, is certainly more important than ever.
If you are going to change the engine on your bike (in this case air/fuel) I would go for something known to make a positive gain, or at least do no harm. As others have said you get what you pay for, which also includes proper testing and recommendations for your specific bike, model and intended use.