You will always struggle with pods, simply because they destroy the ability of the carbs to mix fuel and air. Instead, it ends up feeding the engine with wet, un-aerated fuel.
The carbs work like this: there are 3 pressures zones in the carb. The bowl is at highest (atmospheric) pressure, due to it having the little breather tubes (which should be routed up underneath the seat, or at the very least, over to the back side of the [missing] airbox where air is still and quiet). The bell area of the carbs (where the pods are now mounted) have slightly lower air pressure, when a proper airbox is used. This air is at a pressure lower than the bowl pressure (reasons explained shortly). The lowest pressure is underneath the slide, on the engine side if it.
When the intake stroke happens (engine sucking in air-fuel mix) it creates a low pressure underneath the slide as sucks in the fuel that is laying there from the previous engine intake cycle. Then, the pressure in this area is lowest and the high pressure in the bowl starts pushing fuel up into the mainjet. As it reaches the emulsifier tubes, the air from the bell area of the carb pushes its way into the emulsifier outer chamber and bubbles the fuel as it rises toward the carb throat. This causes it to spray upward, against the bottom of the slide, and wets the area. The next engine intake stroke sucks this mixture into the engine, and this cycle starts again.
When pods are used (or improperly-designed velocity stacks), the bell area of the carb is at the same pressure as the bowl. This means that when the engine sucks in the fuel, the bowl pushes fuel up, but the emulsifier, at the same pressure as the bowl, fights the flow of the fuel. The result is often a lean mix until the upper RPM ranges are reached, at which point there is much more steady vacuum in the carb throat and whatever fuel reaches the area is caught in a turbulent situation, so it aerates somewhat better - but, not as well as if it was first aerated in the emulsifier, so power is less.
The results of pods is always the same story: at engine speeds around 1500-2500 RPM the engine runs very, very 'rich' (which in actuality is a proper amount of fuel, but not aerated, so it won't burn), fouling plugs and acting poorly (and it stinks of gas...), and at around 3000-3500 RPM it starts to improve, but then, as it is also leaning out the mixture here it feels like it is 'falling on its face', so people try to increase the mainjet to stop this sensation (people like to call this "rejetting for pods"). This just further increase the richness to a higher RPM, like 5000, and unless the bike is ridden very hard, all the time, the plugs will foul from far too much fuel.
I have lost count of how many bikes I have magically "fixed" by either removing the pods and reinstalling a properly-designed airbox, or in some cases I have literally blocked off 80% of the pod faces with duct tape (or other media) and put the stock mainjets back in. The bike suddenly behaves again, runs normally (or nearly so), and stops fouling plugs every week.
It's just physics! There must be 3 different pressures in these carbs to make them work: pods only allow for 2.
