Well I'll start off by saying that I didn't think my bike was running poorly after installing my exhaust. I actually didn't notice a difference from stock at all, although I had only had the bike 6 days at that point and was still babying it.
Boy was I wrong.
If the bike was at a 100 before (because I thought it was), it's at a 120-130 now. Nearly every aspect of what the engine done is noticeably better. The first thing I noticed was how much smoother it is when going from off throttle to on throttle. It wasn't jerky before and I didn't think it had any fueling issues like the FZ was plagued with, but it's just so much better now. Getting on the throttle mid corner with the bike leaned over is so much more confidence inspiring. Additionally, and maybe related, is that throttle sensitivity at low throttle is much improved. Compared to how it is now, before it was like the throttle was either at 20% or 0% with nothing in between and now all of that range is usable and smooth. I rode pretty much entirely in A mode last night where I would hardly ever use it before.
The next biggest difference is mid to high rpm at mid to high throttle. It delivers power smoother, stronger, and it sounds... better? Cleaner? Idk, but it sounds healthier. Maybe because of this, shifting up under mid to hard acceleration is cleaner. I found myself wanting an adjustable clutch lever so the friction point could be closer in because the bike is ready to go with power sooner than it was before. Blipping the throttle on downshifts was easier and a bit quicker as well.
Things that haven't improved: engine braking. I know this is a personal preference kind of thing, but I still wish it didn't engine brake as hard in gears 1-3. The only downside about using the Graves file is that everything except ecu settings is hidden and unadjustable, so it's not like I can dial in less engine braking on my own. The only thing I can mess with is top speed limiter, disabling AIS, defaulting to A mode, and fan temps.
None of the changes here are drastic, but combined they make a huge difference in the bike's character. Like I said, I didn't think anything was wrong with it before, but I can just tell that the engine is much much happier now. Would it be worth it to get a similar but more customized tune from vcycylenut for $200? Yes, absolutely. Heck, it's even worth it if you go my direction with the bench kit for $450. If the thing standing between you and an exhaust is waiting on confirmation of a good tune, you don't have to wait any longer.
I think I covered everything but I'd be happy to answer questions about anything else.