that means you need more oil. it could also be a sticky lifter or slightly bent push rod or even the tappets out of adjustment
loose exhaust
can you elaborate? engine noise? stationary/moving? ticking, tapping or a definite knocking?
Engine noise (tapping) than Rap and finally engine seizure
Normal for the 1.8t
Unless you can replicate the engine noise with throttle manipualtion by varying engine speed to 1200 to 1800 rpm, you have a driveline noise
cold engine
Have someone check your Engine mount
Possibly warped brake rotor/worn brake pads. Get this checked out.
It COULD be caused from the lifters bleeding down after the enginge has set for 2 months. Lifters make a tapping type of sound. Oil has a tendency to drain away from parts after sitting for a while.. It may even be your bearings were making noise. Bearing make a knocking..hard rapping type of sound. If the noise went away after a short time, it ain't no biggie. If it still makes noise you may want to have a tech inspect it.
If the 1999 Suburban noise is a sort of loud banging noise, the problem could be that the engine have jumped time. Jumping time would cause the noise and jerking in the engine.
Running too lean.
I ask the same question to GM and they told me that it is a cold motor piston slap and should go away once the motor is warmed up. The garage told me that it is normal and not to worry.