engine miss

hey guys i bought a 99 cobra with 95k on it a few months back and have noticed an issue with it. it has miss/hesitation @ around 2k and 3k but its only when the a/c is on. if its off its fine. it seems its always @ the same rpm every time too. it has also died @ a stop sign a few times before. i cleaned the maf and no change. sprayed carb cleaner looking for vac leaks and no success any other ways to check for vac leaks? any other ideas what may be wrong? the engine mods are k&n cold air, diablosport tuner with a custom dynotune from previous owner. its odd though because only when the ac is going.

i am going to crawl under and see if the fuel filter looks like it has been changed resently and im going to change the plugs too.

The few plugs i looked at looked fine. when i first got it i pulled out a couple to see how they were. this was before i ever noticed this issue. ill check the COPs over when i change them too. they are motorcraft platinums. going to switch over to some copper 764s. its unusual that it only happens when i have the ac on. im home sick so as soon as i feel better ima change the plugs and check the filter and COPs etc. just hoping someone would have some thoughts