I have flashed my bike as well, and it was a significant help, as everyone knows... But it did not fix the bad off idle lean fueling. a friend recommended the Booster Plug
Go here:
https://www.boosterplug.com/shop/frontpage.html
If you go to the site, there is a free 40 page book offered for free that explains everything you ever wanted to know, and more, about bike fuel injection, and how and why Fi bikes are delivered running very lean in aid of meeting certain standards. Because they are set so lean, and because bikes have relatively light weight fly wheels... The off idle and rapid shifting fueling is terrible. This is particularly bad on our FJ-09s. The Booster plug is a gadget that works along with the air intake sensor (Not effected by flashing) to correct the the fueling issue-all explained in the free book. And it is easy to instal. There pieces of body work, and one connector.
What I once thought of a a pretty good bike with crap off idle fueling, is now a very good bike with no... NONE, off idle stumble. It is like riding a carburetor bike. I can now ride calmly at walking speed without using the clutch, shifting in tight corners is smoothed out, and now, all three modes actually make sense.
The unit is unconditionally guaranteed so they do a refund if you are unsatisfied. I was skeptical of course, until I hooked it up and went riding... this is really a fantastic change for the better. In fact, I was very close to simply selling the bike and going to something else because of the frustrating low speed stumble and difficulty in riding slowly... But that is now simply gone. The bike runs better all around as fueling is now so smooth.
One thing... Because this unit effects the way the air temp sensor works, your dash meter thermometer will show 35 degreed F low. I simply bought a small stick on unit to take it's place.
I am not affiliated with this company, but the product is so good I wish I was!
Seriously, if the off idle stumble is as frustrating to you as it was to me, give this unit a try. It simply works as advertised.