I just bought a 2004 WRX with 80k miles on it. It seems like a good car except when I give it full throttle, I can hear the turbo go full speed but then slow down then go full speed then slow down etc. I don't alter the throttle at all when this occurs. You can feel the acceleration changing, too.
Not sure what other info could be useful. The car was in Phoenix it's whole life and now it's in Montana. I think it will do it in all gears but it's hard to notice in 1st, 2nd, & 3rd, easy to notice in 4th and easier to notice in 5th.
I'm wondering if it's not getting enough fuel so the turbo automatically slows down. I really have no idea and all my searches for info come up with zero results. Any help would be much appreciated.
Also, my car is completely stock.