Ok, so I fell victim to the hesitation under acceleration problem, as many of you have. My plugs were fouled due to the Stage 2 tune being so rich. When it first started I replaced my cat with a high flow, helped alot at first but didn't cure it. I changed my fuel filter because I did have a couple tanks of crap gas, that did nothing.
It started getting worse so that it didn't affect acceleration only, it affected starting as well. The car would initially start and die instantly, then the second time it would start and stumble, rev high, stumble, and then eventually get itself together and hold a decent idle, though it would jump around a bit still.
My car has only 7k miles on it, Stage 2 has been on since 3k miles. The plugs looked very carbon fouled, they were covered with the same stuff as you'll find on your tail pipe, if you are running rich. The tip of the plug looked the same brown as rust.

 

sounds about right to me
did you get it tuned after the install of the stage 2?

 

the dealership did it....so it has the GM reflash/tune. I'm sure the plugs are going to foul out again in another 2-3k miles....but at least I found the culprit. I just figured I'd share my story for others that have had the same problems and may have overlooked the plugs, just like I did.

My car also threw a CEL today...it said something about the catalyst system, basically my car doesn't like the magnaflow high-flo cat that I got in my ZZP 3" downpipe.

 

were they dark color? or light brown?

because that light brown "rust" type color is normal

 

Yeah being "rust" colored means the plugs are running the way they are supposed to. If they are dark almost black that a definate rich condition.

Also were you/are you running the stock plugs? You can run the stock plugs with stage 2, but the car seems to run much better if you swap them with some better ones.

 

i have had stg 2 on for 10k miles and problems like you are talking about... possibly something else

 

To do a proper plug test you must drive the car rev it to around 4 to 5 k and shut it off and coast to a stop and then check them ,otherwise they will be carboned up from idling.
The tan color is normal and the carbon on them from idling would be normal as well.

Its not the plugs unless you have a bad one.
could be a dirty injector or a dirty throttle body
or a slight vaccum leak. The routing of the hoses in these cars is really bad.