I will never agree the stock airbox is bad on CV carbs, it shows a misunderstanding of what is going on there. The pulsing back and forth due to all carbs pulling on a common resonating air mass that is semi-trapped in by a paper air filter helps the individual carbs to run slide vacuum up higher, you lose 100% of that sharing thing with pods. It's not just a restriction issue and taping pods doesn't touch that. Direct lift type carbs don't feel that nearly so much as CVs and these being labyrinth CV type with no rubber diaphragms are absolutely even bitchier about it. They leak part of the vacuum created in slide the whole time they operate, like having a torn diaphragm on others. Why pods are a problem on these. Drive with them really fine tuned and you still make virtually the same power as with the stock airbox. But put airbox back on after a while to get used to the pods and you will instantly feel a low rpm torque hit that the pods do not have.
The pods most definitely do not care for stock exhaust, that makes it even harder to tune them in. They like a good flowing header. What jet are you running?, the sputtering says pig rich, the slides are not opening fully or fast enough, what the pods do. Drilling holes can help open them faster but no effect on total amount lifted, that is determined by absolute engine condition, engine down on ring/valve seal does NOT open slides as much, then the pods utterly kill it. Can't emphasize that enough. Why most people have issues, they refuse to look at the motor itself.
On a good tight 750 motor 75P-115S jets work well with a header. Taping them up is silly, may as well put the airbox back on and pick up the lost power then. Taping too much and you just increased the jets, same thing. Wrong, wrong. Bigger jets AND taped?, Have fun with that..............oh, you already have.
Go to the Dynojet website and scrounge around in stage 1 installation instructions to find the exact drillbit size to drill slides with, and completely ignore than you must have their kit to make that work, it's bullsh-t. The slides don't open smoother, that's worthless, drilled, they work FASTER, the lag produces a temporary rich spot that freaks the motor out. After that it's everything you can to get them to open FULLY, nothing really you can do there but one rock solid rule to NOT IGNORE..........these CVs open slides most and fastest when slightly LEAN. Any rich at all and they immediately drop based on how much, any dropping then produces MORE rich due to increased pull because of smaller venturi, etc........beginning to get an idea of what your sputter is??? A quick look behind the bike should show black smoke from it.
Even as simple a thing as valve adjustment can make the pods more problematic, these engines are known for being freaky to set valves on, you set looking for .005" instead of the service manual spec of .003", the engines commonly burn valves at .002" from them held open while running. What you get at engine stopped and checking carefully is NOT what engine sees at rpm. Valve barely not closed and the pods then drive you nuts and how most of these end up, burned valves from not set right.
Engine condition is EVERYTHING to making pods work on these. Done right they will run fine but still may have trouble getting over 8500 rpm in high gear due to slides still not opening 100% of the way, maybe 90%. Engine should be able to run sparkling clean all the way up to 9500+ in all the other gears though. BTDT.