1989 740 Turbo Low Boost

My '89 740 Turbo only boosts to about a quarter into the yellow zone on my stock vacuum/boost gauge. I'm pretty sure I have no vacuum leaks, and my waste gate is in fact connected properly. What could my problem be? Thanks.

Is the waste gate stuck open? Leak in ducting or intercooler?

Waste gate is not stuck open. How do I go about checking for intercooler leaks/ other boost leaks? Ducting has no holes and is tight.

If there's no power draw, it's likely the hose to the gauge or the gauge itself. If you're dogging on power it will be noisy where there's a leak (only really noticeable when boosting) you can spray brake cleaner along the intercooler while running, go big slow swipes it'll take a second to change the idle. Is your wastegate arm adjustable?

Cracks in the turbine housing will cause this. Pull the downpipe and look in there with a mirror.

Torn CBV. It's a TD05-12B I assume? Or Garrett T3?

Pressurize the intake system and get spray with soapy water. Figure out where you want to start testing from, insert the appropriate sized PVC cap, thread a nipple in there, and shoot compressed air into the system from an air compressor. Usually i dump in 15 psi and start lookin for foaming bubbles. Virtually guarantee that you'll find a few little leaks this way. You are lookin for something more significant though. CBV??