09 Acadia random misfires, 3, 5 and 6....vibrates for a few secs upon start.

I have owned my Acadia for about a year, with numerous problems.   Ive
already had to replace the Catalytic converter, 3 coils and all spark plugs.  
Recently my vehicle started to stutter and surge when driving.  It will also
seem to bog down CONSIDERABLY when making turns left or right.  Upon
start up of the car it will vibrate and rapidly click almost like a chain loose on
a 10 speed bicycle for a few seconds then goes away.  In my search for
answers I have found that this vehicle has over 130 TSB's on numerous
parts/functions that seem to be very expensive to repair.  I am dropping my
car off at the GMC dealer tomorrow for further diagnostics as I have found
out that GMC extended the power-train warranty for all these issues.   How
can GMC continue to allow such a faulty vehicles to be sold??  The dealer
will also charge me for the diagnostics if they find out it is unrelated to a
known timing chain/waveplate issue.  Im also responsible for a rental until
my vehicle is fixed, IF its deemed to be related.   Horrible customer service,
I will never buy a GM product again.  Has anyone had similar issue and
what was the outcome???  thanks!