Had to have the Bonneville tuned up last week, did most of it myself.
I let the Pontiac dealer talk me into letting him decarbonize the engine.
It set me back $150... I don't really notice a difference that the tune up wouldn't have accomplished anyway.

Anyone had experiance with this, good or bad, did I get screwed out of the $150 or is this something that'* legit?

If it'* legit then why do we spen money on the aftermarket fuel additives for cleaning the fuel system?