completely unrelated to auto, but ill add a few things if they wernt mentioned..
for 9 yrs, im a certified hvac tech.. ive seen a few symptoms here and there.. that said, im not an r134A tech..(but i passed certification)
bogging the engine sounds like compressor failure. only that will pull enough noticeable resistance to bog the motor.. suprised the belt hasnt squealed.
Anyways, those charge canisters are kinda ridiculous.
i spent my days measuring superheat/subcooling to get residential systems charged properly..
That said, you need a gauge on the system to see whats happening. otherwise you can guess at 4 different problems.
TXV/ compressor/ condenser fan motor/ evaporator filter(if applied)