If you're looking to test for boost leaks the easiest way I think of doing so is using a air compressor (or even a bike pump) on the hose that leads from the throttle inlet tube to the vacuum connection to the right of the intake manifold. What I do is:
1. Remove this hose and duct tape to open port on the gated valve (ejector).
2. Remove the intake pipe from the MAF and cover it with either duct tape or a 3" pipe test cap and use the hose clamp to secure it inplace.
3. Remove the hose from the PTC on the intake pipe and cover the open port on the PTC with duct tape using the hose clamp to secure it inplace.
4. Remove the oil filler cap
5. Insert the compressor fitting into the 3/8" hose from the turbo inlet pipe and pressurize the system to 5psi - 10psi max.
6. Listen for leaks and remedy any issues.
You will naturally lose pressure through the system as the valves will leak, so if you hear any hissing from the oil filler cap or area and are noticing a slight pressure loss that's acceptable, but any other leaks should be easy to distinguish.
This test excludes the PCV system. If you want to pressurize the whole system skip step 2-4, just make sure you keep the pressure to
5psi max as you will be pressurizing the block as well and
will damage seals if too much pressure is applied.
As for common leaks, I've noticed leaks where the injectors seal on the manifold (new seals and seats), from the IAT/MAP (used RTV to seal it), from the CBV cover, loose clamps, and split hoses
Good Luck
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