Best for what? Those are 2 different things altogether.
An oil seperator stops oil getting into the inlet and an egr delete tidies up the engine bay and stops exhaust gasses being recirculated.
The PCV and EGR systems don't add or take away from performance. If you have emissions testing in your area, keep them on. You will fail if these are removed. If emissions are not required, remove the PCV system and add breather or a catch can. I used a Jegs catch can...
I thought I read on here or else where that once you put a breather on the crank fill port you gotta have a tune done. Please tell me that is 100% wrong
This is off RWTD's site... (one of the best tuners for the Lightning around)
"#3: NEVER install a crankcase breather in place of your PCV system. This allows for unmetered air to enter the system, which will lean the engine out. A rule to this exception is a completed sealed off dual crankcase breather system (a filter on each valve cover). If you're trying to keep oil out of your intake, consider installing a 1-way aircraft quality checkvalve right off your PCV."
All the PCV does is vent the oil fumes back into the intake to get burned. Ford put it there the help the enviroment out. Thats it.
There are no sensors or electronics associated with the PCV system therefore you do not need to retune or turn anything off. I have been runningmy set-up for almost 4 months with a few trips to the track. No problems at all.
only downside is after a few wot runs, little bit of oil comes out of the breathers, but better than into the intercooler. you will need to turn the egr off through a handheld though.