Little

I've been looking for what seems to be a pretty good leak in my ac system. From what I remember from last year, I fully charged the system but in 2 or 3 days the system was completely empty again. I didn't bother trying to fix after that as money was super tight but I'm at it again this year. Yesterday I put a small can of the dye in with a full 12oz can of R134 to get the compressor to run for a few minutes to try and circulate the dye. I have the expansion valve exposed as well as all of the other lines that I could and waited for night time to look for the leaks with my light. I went over it a few times and cannot see anything. I also checked the evaporator drain tube for dye and or oil and nothing there either, completely dry. I've gone over the condenser the best that I can and do not see anything there either. I do however hear a low hissing sound from the condenser from only one section towards the middle but I don't see anything. Of course the sound could be just inside the tubes making noise and not leaking. Could I have a micro leak in the condenser that just will not show the dye? Where do I look next? I Intend to bring the car to my shop and pull a vacuum and see how long it holds sometime today. I also did a diagnostic with the numbers below:

Error Codes:
B1234 sun sensor
B1235 Emissions sensor

#1 In car temp (87-89)
#2 Outside Temp (78)
#3 Heater Core Temp sensor, Left (87)
#4 Heater Core Temp Sensor, Right (87)
#5 Evaporator Temp Sensor (87)
#6 ECT Sensor (179)
#7 Refrig pressure (04)
#8 Refrig temp sensor (82)

Theses number have nothing to do with the leak obviously but figured I would post them.
The refrig pressure is obviously low as I installed only one can on a completely empty system and it leaked down over night. I completely forgot to run the diagnostics last night which would have told me how much pressure I lost overnight.

Rich's 97 E420

I also have a slow leak and we do hvac for a living and am having some problems finding the leak. have ruled out the evaporator coil.going to check the compressor seal more closely tomorrow. usually where there is a leak there is an oil residue.