Originally Posted by m5james

Cold idle, yes. After it's warmed it, the only difference I notice is a little drone when the truck is trying to hold a high gear going uphills. The exhaust system is pieced together from what MSR does on his new custom exhaust system, but since they only make M5/M6 stuff, he told me what they use. F10M5Manual told me it's got zero drone but you can really hear the turbos out back, so I can only hope it'll sound the same on an X5M. Having done a resonator delete and Magnaflow mufflers on my 740iL with drone so terrible that it sounded like a speedboat on the streets, I've learned my lesson and won't keep any system if it drones too much