My story was very similar. I bought my replacement boot at FCP. It was OEM, but I had to stretch it, which caused a big kink and loose of power. I spoke with FCP and they were surprised to hear and we're not able to help me. They checked p/n several times and told me that they will find out. I waited two weeks, did not get an answer from help and decided to try a local dealer.
Boot that I got from dealer worked great! I had no problems of installing it and it looked significantly longer.
Sent from my SM-G900V using Tapatalk