Ok, truck runs fine, no issues with backfiring or really poor mileage. Supposed fresh timing chain and head on the truck within the last year. No receipts to prove it. Recently I noticed a rattle noise while accelerating above 3k RPM and when I downshift (regardless of RPM) it makes the same noise briefly. Im fairly new to Toyotas. Does this sound like anything specific or is it just a case of checking my timing chain guides and adjusting the valves? 302k on the clock so Im leary of bottom end issues and every little noise raises my awareness. It also has a taping/rattle at idle that seems the loudest when laying directly under the cat. Im stumped and dont want to throw parts at the truck. I appreciate any and all help.