Re: air-con problem
when the compressor is working it is a drain on the engine, the engine management is designed to automatically switch off the compressor when the engine needs full power (under full load), but under all other circumstances you will notice the engine stuggle, this is especially so at low rpm. on many cars with a/c you notice the car struggle when you try to pull away with the a/c on full blast, then the engine suddenly picks up after a few thousand rpm when the compressor is switched off. this is normal behaviour.
you say "it still isnt working properly at all", are you not happy with the temperature or amount of airflow? on the 156 there is less airflow than on most other cars and this can make new 156 owners think there is a problem. also it can take a few minutes for the a/c to achieve cold air.
the best thing to do is set your fan to auto and select a temperature, then let the climate control do the rest, it should maintain a cabin temperature for you, adjusting the fan speed and a/c compressor usage as required.