Hello, I have an 02 wrx and for some reason in 4th and 5th gear between 80 and 110mph my boost will constantly fluctuate between 17 and 4 psi. But after about 110mph it'll stay at around a constant 11-12 or so psi. Does anyone know what would cause this? And am I able to fix it without getting another tune because I don't have $900 to drop on a tune right now. Thank you for the help.