It had recent turbocharger replacement, and there is a whistling which sounds like sirens following me when l drive; Can an air leak cause both problems? Is the gauge mechanical or electronic, and should l hook up an aftermarket mechanical gauge to verify boost or is there a way l can check to see if the stock gauge is working? thanks gang!

a faulty sending unit for the guage

The whistling is your blow off valve, you need it when you get a turbocharger.

you probably have a broken vacuum line, check them all closely, not all turbos use a blow-off valve