So after I put my BBK off road x pipe on my 01 Cobra I started hearing this rattling noise, thinking it was exhaust I took it to the shop and it wasn't, I even checked, so this only happens at like 2000 RPM and up once the car is turned on for a few seconds, and only when I give it gas, not when I let it engine brake or idle. So I'm thinking Rod knock but wouldn't that be all the time? Oh and I've been running 91 octane on the engines 93 octane tune. So I just ordered a bama 91 octane tune and new spark plugs? Maybe that'll fix it? What does it sound to you guys, thanks.