I worked on a system 2 weeks ago that had a leak. I evacuated the system and charged with nitrogen but could not find the leak. This is a 5 ton ac only system with about a 100ft line set which is not accessible for about 50ft. I had not found this website at that time and didn't know any better, so as a last ditch effort I put in a can of the HVAC/R Super sucks.
Well the system was fine for a week until yesterday when I got the call for no cooling.
I had to replace the drier today . I'm going to cut it open tomorrow and see if I can get some pictures.
I only wish I would have found this website and read some of the views about it here.