I recently bought a 2008 Cadillac CTS 3.6L Direct Injection. Has 120000 miles. Changing all filters just because and I can not find the fuel filter. Yes it’s supposed to be rear left inside frame. I’ve changed many GM filters through the years. Traced the fuel lines and no in-line filter. Must be something in Tank??? Owners manual says nothing about a fuel filter. Must not be one that’s serviceable