Is there anyway of bypassing this?

 

Yes I heard that slowing down how fast the engine drops rpm = better emissions. Something about snapping the throttle closed causes high hydrocarbons while the rpm drops back down.

Not that I know of. It is part of the computer/drive-by-wire setup from the factory.

I read about it in some mag when the car first came out. In order to get emissions certified GM had to find some tricks to meet requirements.
Supposedly snapping the throttle closed causes a temporary over-rich mixture that jacks the hydrocarbons substantially, so the computer slows down how fast the throttle body closes.
I hardly notice it any more even though I didn't like it when the car was new. Maybe it changes as the computer adjusts itself over time?

I don't know if a custom tune would be able to change this parameter. Anyone know?