Oil supply and drain
Use the correct oil and change it regularly. A restricted oil feed can damage bearings. A poor oil drain can cause smoking and seal issues. The drain should flow downhill without kinks, tight bends or crankcase pressure fighting it.
Air filtration
Compressor wheels do not like dirt. A quality air filter and sealed intake path protect the turbo and engine. Check for loose clamps, rubbing pipes and dust tracks that suggest unfiltered air is getting in.
Boost leak checks
Boost leaks reduce power, increase turbo workload and can confuse tuning. Pressure testing the intake system is a simple way to find split hoses, loose clamps, leaking intercoolers and valve issues.
Warning signs
Whining, scraping, smoke, sudden oil use, excessive shaft play, slow spool, metal in piping or repeated boost control issues deserve attention. Do not keep driving hard and hope it clears itself.