Uneven acceleration/hesitation with A/C
 

I have an 08 with 124,500 miles on it. It's a 5 speed manual, with original clutch. There are two problems: firstly, when car is at idle and the A/C on, the engine hesitates ever so slightly. I initially thought it was the compressor and/or the system was low on freon. However, I had it looked at, twice. Once, the system was emptied and refilled to spec and I took it in again for a recheck. The compressor doesn't kick off and one, but appears to be constantly engaged.
Secondly, when accelerating or placing engine under load, there is an unevenness to the engine. If feels a tad like a misfire or vacuum leak though I cannot smell any fumes. Any suggestions?
Plugs were changed about 20k miles ago and the valves adjusted too (though I have a mean valve tap)

What about the accessories belt for AC, has it been changed or looked at recently, or its associated components?
My bad if our Fits dont use a belt. :D