2007 Camry air brake noise after replacing timing Chain

2007 Camry SE 2.4L 4-vyl DOHC (Mfi)
Engine appeared to be running fine but had code P0016.
Changed oil and Oil filter.
Replaced Camshaft Position Sensor.
Replaced Variable Valve Timing (VVT) sensor.
Crankshaft Position Sensor.

Code still there. Took it into shop. Shop said timing chain stretched and slightly off giving the code. I replaced timing chain. Upon startup of engine there is a sound, similar to that of an air brake releasing. To my ear it sounds like a release of compression. This happens once and then the engine idles without any problem. Increase RPM’s, the air brake sound returns and continues until return to idle then no air brake sound. Went back to double check if timing set correctly. Crank pully at zero, No. 1 cylinder all the way to top (put 3/8 extension in cylinder and watched it go to top), both intake and exhaust valves closed, markings on intake and exhaust gears match small arrows on top of cam caps.

Any Ideas what that sound is and why. Engine ran fine before replace timing chain.

Thanks

Tom