Hi, I have a 2006 XLT 4.0L v6 explorer that was stock, until I recently installed a custom dual exhaust on it (AMAZING sound), along with a KKM air intake. I have noticed that after the installation of the KKM intake, there is a whistling sound whenever I push on the accelerator. It is super high pitched and super annoying. I have read some threads on here, and apparently the whistle is a common problem on the v6 4.0. Has anyone ever successfully fixed this problem? It seems as though no one has figured out how to fix it. Also, how important/useful/much performance would be gained by installing a heat shield? Thanks in advance.