Interesting thread. I had a walbro 255 in my wrx and it never once whined and I put 50K + miles on it.

I installed one in the Evo today.....start the car and everything is good. No noise, afr 14.7. Then after about 2 mins the car started to sputter. I get in and the pump is whining loud as hell and the afr is in the 17's. I thought hmmm.....weird. I went for a drive around the block. Afr went to 21 and I barely made it down the street. The car died when I tried to let it idle. Its dark so I will have to mess with it tomorrow.

I have a theory I'm going to check. The walbro is slightly shorter than the stocker. I'm wondering if the top of the pump popped away from the top hat and then slowly pulled off. If so that would explain the lean afr as well as the whine.

Again, my wrx NEVER whined with the same pump.