I dont know if mine was missing anything, but there are 4 bolts and accompanying nuts on the flange, and that is all. I dont know what grommets there are (I am curious to know what I dont have).
For me, with the stock Mac oval air filter, I have to install it from below the car. The pipe is long enough that I have to have it unbolted from the TB and finagle the filter onto the pipe (which wants to slide around up top) and then cinch the filter and attach the pipe on top.
I want to get a small conical filter which fits through the hole in the fender so it can all be snaked out from on top.
Good luck