something that goes quite a way to fixing it is a piping kit between turbo and intercooler and a twin entry intercooler , so you keep the compressed air from each turbo seperate till it exits the intercooler . it is a common problem with that size turbo , as you know but I have had it on non ball bearing turbos but not as bad , a friend of mine has also had the same problem , I fixed it by going single turbo , that is te cheapest upgrade that will completely eliminate the problem , I think JMS have a couple of used single kits for reasonable money .