Rogerius has a good point. On our cars if the intercooler hoses arent attactched securely, you can get a stuttering noise. I was left stranded at a gas station an hour and a half away from home. When I was passing a car on the interstate, I blew a hose. I didnt know anything about it but Ill check things out next time if it happens again.
Vacuum hoses, DV, and intercooler hoses are something to check if you are stuttering and loosing boost. If you take the DV out and compress it, is the spring stiff? If so, its possible that the diaphram inside is broken, and you are only left to replace it.
Forge's arent known to fail, and if they do, they can be rebuilt.
Steve