Need some help diagnosing this sound! Only happens in Park and when I let off the gas or going down hills. For context, we just replaced the header today and didn’t have a donut gasket for the flange between the header and the down pipe. I’ve also sprayed around the injectors and nothing changed. I messed around with the TB and nothing changed. And for the life of me I can’t find any lose hoses or bolts. Thanks for any help!