Was the mower designed to be a mulching mower? If no, then the mower was designed to throw the cut grass toward what was once an exit chute. Simply adding a mulching blade and covering the hole won't turn it into a good mulcher.

roadbike is right. Your mulching plate probably should have had a lip to catch and direct clippings back into the cutting path.

I was afraid that was going to be the answer, but it is what it is I guess, and time to get another mower :>) Thanks for your help!!

Are the blades new? If not are they sharpened?

Get a Gator Blade and remove the "mulch cover." It will still throw the grass out the side, but hopefully in smaller pieces.