The inconnel is awesome, and very nice looking. I significantly reduced the temp on the interior of my car, the side sill and of the incoming a/c temperature.
I did a header shield, inner and outer sill shields plus a tube that covers the entire side exhaust then the "factory type" inconnel goes in too. The difference is amazing.
You will always have heat soak when the car gets parked, but my car used to get to the point that my wife didn't want to cruise because it got so hot on the side by your legs. Now that stays cool to the touch and much more heat exits the car at the rear. I moved my tips out another 2" to get the heat away from the rear fascia since so much more is exiting the rear with all the shielding I have.
The inconnel is used in Indy car applications, military applications. Good for like 2000 degrees F sustained temp.
My factory insulation, a low grade of stainless...not aluminum...melted through at the cats and the fiberglass inside was melted too. That crap was virtually useless for heat insulating when I removed it. I heard that the factory stuff starts to break down in a few thousand miles.
Talk to some of the people that installed the inconnel in California and you will find out it is the most trick stuff you can buy. The price of the raw material is very high, and the quality of the custom pieces is awesome...thus the price is high.
However, if it keeps my car from breaking down components like plastics and paint color, a few thousand dollars is cheap.
I ran bellanger headers without heat shields, bull crap. Listen to Viper Wizard Chuck and install heat shields. Do your car a favor.
Just my personal experience and opinion.