Someone I know has a 2011 Impala, 3.5l V6. Goals are to slightly improve throttle response in relation to a flat spot, and possibly improve fuel mileage to some extent to hopefully net a return to justify the expense. Not because racecar, but wants to just try to get rid of the flat spot it seems to have.
Software? Are there any tuners or reflashes that would be advised or avoided? Any advice is appreciated.
Thanks
Edit: Actually its not going to be worth it with a V6
I would have said HP tuners but there is a learning curve and your not going to save enough in gas etc to make up the difference in the tuner price.
Check the Impala forum? http://www.impalaforums.com
HP Tuners supports that car and would be by far the best option for tuning. We offer custom tuning with HP tuners, however it is a flat rate custom tune ($350)
+1 on getting someone else to tune it 
That way you don’t front the cost of the tuning software/programmer and its not like your going to keep modding it.
I would help you out, but I need to buy a battery for my lap top. I’ve been lazy and keep putting it off…
Watch the ECU on these things, some have one similar to the V6 CTS where you can’t access much of anything in the trans.
Flat spot could be a bad pedal assembly or throttle body. I would check both of those out before spending money on tuning. Also you might want to check if there is a GM update for the PCM & TCM. A lot of times GM releases software updates to address these problems and most local shops will only charge $75 for a reflash from the AC Delco TIS site via a Tech2 or GM MDI interface