90% of the oily fumes pass through the PCV system on the driver's side of the car.
If you are only going to have one it needs to be on the driver's side.
The clean side line on the passenger side has a sensor in it. You will trip a code if you put a catch can on that line. But, Ford Performance has come out with a catch can for both sides. The passenger side one has a sensor in the line they provide. Presumably it addresses the code issue.
Your other choice is one of the dual valve catch cans like the one from UPR that through the clever use of check valves and the low pressure point in front of the turbo will pull the oily fumes through the PCV system on the driver's side whether you are on boost or off boost. This unit happens to mount on the passenger side but is not part of the clean side line.
I added the JLT dirty side oil separator after flashing the ECU for this reason. The stock tune can compensate for low octane events but a tuned ECU requires a more consistent and higher level of octane. Low octane events when tuned can contribute to ecoboom via detonation, pre-ignition, etc. A flashed ECU will increase torque so there will be increased blow by and therefore more octane dilution at the precise time when octane is most important. At least that is my theory based on what I have read. After 500 miles I have about a shot glass of sludge collected in the can.Less oil fumes/sludge in the intake charge keeps from diluting the fuel octane also
Ford performance recommends adding an oil separator with a tune. This is from the 2015-17 Ford Performance website.Thank you for the analysis and insight. In past years since the introduction of the EB Mustang, dealers were not recommending catch cans or air/fuel induction cleaning. When I bought my 2018 EB the dealer did not recommend an oil catch can when I asked. Since I installed a Cobb Stage one tune, I believed a catch can was necessary. At the time of my last oil change this month, the technician discussed a air/fuel induction service. I think Ford has finally caught on.
You do not need the dealer to install the FP tune to keep the warranty, just an ASE Certified technician. I would recommend a local performance shop over a dealer. They do this type of work all the time and are going to be more experienced and cheaper.The dealer I bought my 2018 Mustang EB from is owned by a large "corporate" investor, not a mom & pop dealership. I asked the Service Manager about a Ford Performance Tune and he did not recommend it and declined to install it. After checking around the Metro Atlanta area, I found most Ford dealers were not performance oriented. One dealer in North Georgia would do the install but they were too far away. Thanks for the info.