I have run mine for 4 seasons with no clamshell or insulation on the pipe. As stated before, it is there to help deaden the sound of the sled. I painted mine with BBQ paint. I have zip tied my headlight wiring and speedo cable out of the way as they both like to rest on the exhaust. It does not run any different at all.
I have two sets of after market pipes slp and aaen and neither have any kind of coating on them and both sleds run just fine. Take the dam insulation off before it wrecks your pipe and be done with it. I think the big reasoning behind the insulation is for noise and under hood heat. Maybe if you notice a peformace losse it cause you just increaced the temp under the hood warm air = less power just a thought anyway.
the sheilds on stock pipes are for under the hood tempature its cheaper to build you will lose no power removeing the shields,the temp under the hood will rise and you will lose power from that,