i got a 03 wrx and recently i've been noticing a rattle when i'm off the gas, but in at around 3k+ rpms, so typically when i'm downshifting to slow down. it's not too loud, but audible especially if i'm next to a wall or something. anyone have that problem?

i also have another problem that started after i noticed the rattle. it's a kind of loud knock sound, just once, when i put my car into reverse and start to move it. it'll come typically within the first few seconds of being in reverse. i don't notice any performance loss, just curious what's the problem and/or if it's symptoms of things to come....?

any help would be appreciated. thanks.

 

could it be the exhaust hanger? or the heatshield?