My question is: What year model is it? You really should add that to your "Drives" info so we can better help you in the future.
If it's still under warranty, I suggest you spend a couple hundred bucks and get a Range Device to kill the AFM without killing your warranty. 10 second plug-n-play install through your Onboard Diagnostics port. If your car is out of warranty, you can get AFM tuned out. If you haven't yet noticed the aggravating sound and lack of power when you car goes into 4-cylinder mode, the previous owner may have had it tuned out.
More Power = More Money... sometimes a lot more. Working with a stock engine, you can significantly improve your cars response and performance by installing a cold air intake and air scoop (I have a CAI, Inc intake and love it - it's by far the most popular brand among Forum members). It will cost you close to $500 but is well worth it. Very easy install.
For about $175 you can get a Vitesse Throttle Controller which really improves throttle response time. This is also plug-n-play and takes about 15-30 minutes to install. I love mine.
And, of course, you have to get rid of the stock exhaust. For my taste, muffler deletes are too loud - I don't like to piss off neighbors, nor would I like them pissing me off. I installed a Solo J-pipe axle-back system. It sounds strong and deep at slower speeds and really roars to life when you stomp on it, yet it is not obnoxious to others. There is also no cabin drone either but the j-pipes will adjust if you like the sound of drone.
Good luck. Welcome to C5. Tell us more about your new ride and, I almost forgot...
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2013 1SS/RS Coupe L99, Stainless Power Works LT Headers, SCT X4 Custom Tune from RDP, CAI Inc. Air Intake w/ Apex Scoop, VMAX CNC Ported Throttle Body, Solo Axle-Back Exhaust w/ J-pipes, Apex Catch Can, Husky Splash Guards, Heritage Grille, 3D Carbon Rear Spoiler, Oracle Chrome Turn Signal Bulbs, GM Reverse Light Trim Billets, Gorilla Black Locking Lugs, Emblem Pros Retro SS Badges/Custom Retro SS Kickplates/Under-hood Bowtie, 35% window Tint, Nitto Motivo Tires (6-8-18)