Zx9R low speed miss

Well the zx9rE trackbike is looking good after a paint job, general tidy up, and a bit of pinstriping.
At Hidden Valley on the weekend, it developed a misfire on partial throttle, and at or just off idle. Once the throttle is opened wide, there is no problem, it is only partial throttle ,coming out of corners, or rolling into them when the miss shows up. Anywhere above half throttle is good, under that and it sounds like one or two cylinders are dead, and there is a lot of backfiring going on that wasn't there before.
Any ideas???
I don't want to go tearing into it,pulling off the tank, airbox and carbs only to learn the igniter or some other part is a known fault[:o)]
Thanks in advance

Sounds like a fuelling issue if it goes away on full throttle.

The emulsion tubes are pressed into the bodies on the zx9e carbs and cant be replaced. They will wear oval over time and produce some spluttering at low revs, but it's normally not too drastic, and would gradually appear, not just overnight.

I'd try a good carb clean and a new fuel filter first up and see if that helps. Could also be fouled / dodgy plugs (it's not unheard of that plugs can fail to fire at certain RPM's).

It was a blocked pilot jet on number four, and the air cleaner element had collapsed, and spewed its ugly crap all through the carbs. All cleaned up [along with the plugs], just got to fire her up after putting the tank back on...tommorrow morning.
Thanks for the advice Hillsy.