I had the same problem when I was installing mine. I could not get the middle clips to catch no matter how hard I pushed or pounded on it. It wasn't until I got really frustrated and smashed it will all my might that they all finally grabbed. Mine has no gap, completely closed all the way across. So maybe you just haven't been firm enough with it?Does your HPD diffuser pop out a little right above the exhaust tips? There are like 4 clips I can't get to attach permanently. It leaves just enough gap to see the ground.