I'm not sure what you mean by "CBV" but your pressure loss is probably nothing more than a hole in an intercooler hose, not unusual in older turbo cars.
Inspect the intercooler hoses looking for evidence like oil as you'll see oil when once splits.
The turbocharger itself is almost bullitproof, a simple device really that can't "fail" unless it's siezed and that's unusual with water cooled turbos (since '87 with Volvo).