A couple more comments:

-I have the PF in my car and I can't think of any drawback besides the nuisance of fabricating custom hoses. Go for it.

-If eveything is going to be new, what is there left to flush? You already have a huge job ahead of you, so don't make it worse than it already will be. Still go for the filter though.

-I stand by my comments on the recirc. door "trick." No disrespect jchyun, and maybe my car is special, but it didn't work. I used your link a year ago to do this mod., and on my car the system would cycle a couple times and then the recirc. door would no longer open and close until I turned the car off. Something in the switch system would not allow my car's doors to open and close as you claimed they would. I drove around for a couple days with the glovebox out just so I could easily observe what was going on and to be sure of my conclusion. If it were my car, I would maybe rig up the electric fan to turn on when the compressor is running, but I wouldn't bother with this particular mod.

-When I did this job the advice given by the guys that sponsor ackits.com was to use Nylog on, and I quote, "everything." O-rings, threads, service valves, service valve caps, etc. It can't hurt.

-Just snug up the fittings with the wrenches. These are all light aluminum fittings, and the o-ring is actually doing the sealing work, so don't go too hard on the fittings.

GregS
'84 300D, 174k
'90 300CE, 164k