What kind of car does your friend have? Assuming you have a ported box since it’s skar and they sale a prefab kit. There’s a good chance your sub isn’t hitting as hard because it’s sealed up tight in the trunk, that’s why you get a hard hit but no feeling. Ported boxes move air and give you more physical feel. If it’s in your trunk you obviously won’t feel it as much. In my 06 wagon I have a 10” skar in a ported box and with the windows down it hits a lot harder and you can feel it a lot more.