Okay, almost 2 weeks later and I've finally gotten to drive with those foam plugs out. Wow, what a difference! I couldn't hear a darn thing different sitting in my garage and revving the engine a bit. Once I got it on the road it sounded so totally different I couldn't believe it.
Ordering some parts from American Muscle tonight. They'll be the first parts I order from them. Or anyone, actually. From their customer service posts I've seen in other threads, looks like they treat their customers right.
2013 GT Premium with Track Pack
"The Devil is in the details, but so is salvation." - Admiral Hyman G. Rickover