You're still getting the same amount of boost but the IP doesn't know it so it doesn't send any more fuel in. Just adding extra air with no extra fuel won't do any good. Sorry don't know the part number.

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Seth

1984 300D 225K
1985 300D Donor body
1985 300D Turbo 165K. Totaled. Donor Engine. It runs!!!
1980 300SD 311K My New Baby.
1979 BMW 633csi 62K+++? Dead odo