Guess it is time we found out the warranty terms of the Street. I know for sure that replacing absolutely anything on the bike will void the warranty. A friend bought the Iron here in Mumbai and opted for different exhausts from the showroom and they void his warranty. In spite of selling and fitting it themselves. Aftermarket is whole other ball game.
Eh, not really, at least in the US. While the Harley Davidson warranty covers the stock exhaust, adding an aftermarket exhaust doesn't automatically void the warranty and depending on the model of bike and the sound level of the exhaust might not even be illegal smog and sound wise. The warranty won't cover what you modify, but the parts you don't modify ought to be covered. In the US at least, the manufacturer would have to prove that something you did is the direct cause of the failure to void the warranty. I put aftermarket shocks and XR-1200 wheels on my Street Rod, drag bars and Night Rod risers too (the dealer is so unfamiliar with that model they think the handlebar and riser set up is stock, lol) but despite the changes they have honored the warranty to replace a swingarm bushing and a couple of fork problems, along with a couple of electrical problems.
The Extended Service Plan doesn't cover the exhaust at all so you can do what you want. The fine print of the ESP says the whole thing is void if you even change the gearing, but I have changed the gearing on my Street Rod and the dealer just looked the other way when the bike had problems covered under the ESP.