how do you remove the grill in the middle of the lower bumper ?

It is held on with clips. If i can find some i'll get some pics of mine when it was off. You will need a flat screwdriver and prise the tabs that hold it. Very similar to the top grill.

thanks ordering an alloy cold air feed funnel to put on the end of my cold air feed pipe, would be easier to take grill out.

You can do it without removing the grill. just put your hands under the bumper.

It's very easy to run the cold air feed done mine not to long ago.

I already have a cold air feed pipe which is almost up against my grill, there may be just enough room between grill and end of pipe (without breaking the zip ties that hold it in place) to add a nice alloy funnel on the end. Taking the grill of would give easy access straight to the end of it otherwise will have to get underneath.