Just replaced the CBV on my '89. The diaphram was broken and prevented the turbo from working. These are not repairable. Don't know what the replacement cost is but they're easy to replace. Just three 10 mm bolts. If you go to the pick-your-part yards be sure to get the right one. The newer ones have a longer section that fits inside the Mitsu' housing. Maybe the valve is broken on yours and leaking. Mine had a bad diaphram and created severe engine hesitation whenever any turbo boost was created.