Misfire and breaking up at 3000rpm

Hey I'm new to tuning. What could be causing a misfire and breakup around 3000rpms?

A bit more info needed please - What engine -ecu - ignition are you running ? boosted or not ? do you have a wideband fitted and at what sort of load is the engine under when its happening ?

Hello here's the additional info. I am going to check my plugs as the misfire isn't consistent. However it is happening more often. Previously it occurred a few times at 3k+ along with the breaking up. It just started happening at a low rpm. The breaking up is consistent. It occurs around 3000rpm underload and at half throttle. I am unable to take it above 3k rpm without breaking up. It is a LS 408 stroker with stock ecu, it is not boosted, I have widebands fitted.

Also, the engine is not responsive to throttle. The afr on throttle is 12.6. But it runs VERY lean at idle 15-17afr.