I found a glitch while using belts with capacity 90+ items\sec (I use Ultimate belts mod):
If you try to set belts with ips > 90 (but I think actually > 100, in this mod there are belts with ips 90 and 120) as input inside the factory or output outside, then some strange things hapens and items start carried over once per ~2 seconds instead of normal
For now I count it as a challenge, but can it be fixed? :D

My code won't work properly once your belt is faster than 120 items per second, or one item per lane per tick. But I'm not gonna fix that, since I don't recommend using fast belt connections anyway. They're not the best for UPS, since each item on a belt needs to be teleported individually. Instead, I suggest that you use chest connections with loaders instead of using belts directly. This way you can use fast belts with Factorissimo with minimal UPS impact.

K, thanks for reply, I'll try that

you can use the express belt miniloaders to load a full blue belt worth of items to chests, and unload at that speed inside as well. allows you to rapidly load and unload while using chests as the teleport method which allows much better UPS utilization. and the mini loaders only take one tile to move fully compressed express belt (45IPS) into and out of chests.