I let myself get snookered into that on a '98 Viper I used to own - did it within months of purchasing the car new. Did the combustion chambers, exhaust ports and headers. Absolutely no difference in running temperatures. Did not have a before / after dyno but "post" dyno numbers were very average for 98 GTS. 438 RWHP (mods were coating, headers, cat-back, smooth tubes) sticks in my mind, but there's a lot of crap kicking around in there these days!