Well I missed the idle is smooth at 750rpm indicated and roughens up when the air compressor is engaged. Some air incoming may still enable that. It has to be eliminated as a posssible cause anyways.

I am starting to think that next is a general check of chain stretch, primary pump timing and valve adjustment. Thats with all possibility of air being a factor gone. If all that checks out then this car is a really good candidate for examination or a scan with the milli volt method in my opinion. This in my opinion is also the best dynamic check of the fuel injectors condition available to us at present. In a nutshell if an engine deviates from equal power strokes as overall designed or the designed function is upset by common wear of timing chains etc. It does not respond well in an equal cylinder to cylinder fashion as load is applied. Even if it is just the load of an air compressor.

I also think marginal motor mounts could contribute as the compressor is a loading factor for the engine.