So i received my hydrocarbon gases, one bottle of R290 one bottle of R600a, superdry and 99.9% pure.
Mixed the following blend:
37% R600 (isobutane) + 63% R290(Propane).
The pressure of the blend at 86 deg F (28deg C) is at 104 psi.
Remark pure R290 propane has a pressure of 135 psi at the same temperature, adding 37% of R600 is reducing the pressure by 30psi.

I filled my Ac with 11.28 ounces (320 gram).
The LS400 usually takes 35.2 ounces (1000gram) of R12 gas.

I could load the complete batch in seconds, without starting the engine.
I started the car, the compressor kicked in, it sounds super smooth, the noise is more like a hisssssss than that grrrrrrr noise i had before, due to the fact that the propane molecule is much bigger than the R12/R134 molecule, thus easier to compress.

My pressure readings: Low side 38psi, High side 150 psi.
With the R12/R134a blend i had 40psi/220psi.

Gotta check out why my low side readings are on the high side in either case, but i belief it is because of the gas mix.
The Lexus specs for R12 are 21-28psi low and 206-213 high.

I am getting a instand duct temperature of 53 degF (12Cels) on a 90 deg (33Celsius) super humid day. The condenser is not only dripping, water was running out the drain hose, i could fill a small coffee cup in about 1.5 minutes.

Once i put the system to recirculation the duct temp drops to 44 degF (7Celsius).

The performance of the system is exactly what i had with my high performance R12/R134a mix, but with much less strain on the compressor, the changes in pressure and compressor noise are obvious.
Not to mention the amount of engine power saved with the mix.

Another thing i noticed, when i switched on the AC at idle with R12 my idle Rpm was noticeably dropping before being raised by the ECU.
Now the idle RPM do not drop.

Propane is the way to go!