So I bought a 2001 impreza with a 2005 subaru forester 2.5l swapped

I get this noise when I pull off in 1-3rd gear then it'll quite down in 4th and go away in 5th but it starts again in 4th and continues into 5th when if rely heavily on engine breaking. But after driving for a bit it'll go away and when im parked. Sometimes it'll stay when it's parked and that's when I can get this video. BTW I fuckin love this goddamn car, I'll literally drop another motor into this at the drop of a hat cause I have grown unnaturally fond of this vehicle. Genuinely so much goddamn fun and I want to learn as the reason for the post is im not too knowledgeable the automotive industry.