I've only had my 2013 WR450F for about 3 months, coming off a KX450F. I rode it with the Comp ECU, but made no changes for the first 2.5 months.
I just got my FI Diagnostic tool and finally got around to changing the CO level (local dealerships had no clue) and playing with the mapping. It DOES make a big difference. I was running pretty hot most of the time and found that it was a little twitchy at low RPM, causing me to have to be way more clutch attentive. Now that I've gone to a different map, its not as twitchy and has a nice mid hit which I like.
It may not be everyones cup of tea, but the mapping changes can make significant differences in the bike. Is it cheap? Not really. You're looking at about $300 for the comp ecu and the power tuner and my FI tool ended up being about $150. But for me, the ability to change so quickly depending where and what I am riding on is worth it to me.
Keep the two wheels facing downward....
Juman, which map changes, FI diagnostic and GYTR power tuner do you have that reduced the bikes twitchyness at lower rpms? I'm playing around with it now and any advice is appreciated.