Bumping this very old thread, I hope it's okey. My Lexus RX300 is throwing P0171/P0174 (lean, both banks) just about every time I refuel. I have checked charcoal canister, fuel cap, hoses, and everything seems alright. Idle is also fine and engine performance doesn't feel down on any way.
Today I unplugged the PCV and it won't rattle and I am able to blow air from both sides (tasted bad on my lips, I hope it's not cancerous) although easier from one side. I put the thing in a ultrasonic cleaner filled with brake cleaner. After 10 minutes the bowl was a black mess.
Now the thing looks brand new and the spring mechanism is working, but I'm still able to blow air from both sides. Sigh. Called the dealership here in Europe and they want $80 for this piece, said it was an old and rare OEM part. I looked it up on Amazon and it looks like the PCV is more like $8 in the US, but unfortunately shopping overseas is very expensive.
I think I'll give it one more time in the ultrasonic cleaner. This time I'll use gasoline instead of brake cleaner, like someone in this thread suggested.