I have a 2004 WRX. The other day, driving down the freeway, I decided to make a hard freeway pull. Running it up to redline in first, second, and third gear everything went fine. Once I shifted in to fourth gear, under full throttle, you could hear the turbo pull full boost, and then spool down to around five or six pounds, and then immediately pick back up to full boost, and then spool down to five or six pounds again. It did this all the way through fourth gear, and all the way through fifth gear. It only does it in fourth and fifth gear. Any help would be appreciated. Thanks.