Need help :(

Hoping someone can help. This all happened about the same time, I developed a boost leak which on light throttle as boost was building it would hiss very loudly then it would seal and stop the hiss and come on boost fine. It's loud and sounds very close so I thought it was my tubing to my boost gauge at first, ended up removing it anyway and putting a big bolt in where the take off was on the hard boost pipe and siliconing around it. Also noticed a soft pop from the engine when I switch it off.

Fast forward to today I bought a new standard top plastic hard pipe off of a guy on here who's name escapes me and changed it thinking it was the bolt I'd screwed through and siliconed that might be leaking. The joint on the top of intercooler had a lot of play even though I'd cable tied them a few months back so went to the bro in laws garage and got the bumper off and double cable tied all the joints. The top intercooler one did have a worn lug but it doesn't move anymore and none of the other joints move apart from the actual one into the turbo but these always have quite abit of movement. Feeling confident I drove home and guess what exactly the same :( all the joints were clean apart from a light misting around the top of the intercooler where the top pipe goes in and the front part of the core but it wasn't fresh and excessively coated. The only other place there's a misting is on the egr, it's mapped out but still in place. Could it leak boost from there and could this problem be causing the pop when I turn it off too? It does sound close to you like it could be from the egr area when you're in driving but can't replicate the hiss when stationary to check. Really did think it would be a pipe but I've cable tied them tight and it's made no difference whatsoever so must be something I've not touched which would be the egr or the actual turbo connector as I didn't take it off there.

Thanks for reading the long essay hope someone else knows what the pop is as the hiss started around the same time so I'm pretty sure it's connected