hi guys I have a 2001 silverado 2wd with 209,000 miles on it i drive it pretty hard and ive noticed a rattling noise at 1800rpm and up if im sitting still and give it gas once it gets to around 1800 rpm it starts to rattle a little bit from the engine bay.

things ive done: i gutted my cats, dual exhaust, new plugs and wires, running 91 octane, bullydog programmer. i just changed the oil with mobil one and it seems to be slightly louder than when i used valvoline. i change my oil every 3000-3500 miles

i drive it hard this rattle has been doing it for a few weeks and i have been driving it and havent noticed any performance issues?
any suggestions are appreciated. thanks

 

Lifters or cracked flexplate.