Automatic Litterbox Central

I am currently using a Litter Robot 2 and have been having a very difficult time regarding odor. The Litter Robot is located on our back porch next to the kitchen and a bathroom and the odor is so strong it stinks up the bathroom and sometimes the kitchen (when it gets really bad.) I use the Ultra Litter Pearls which worked well with the odor when I had one of the regular litter boxes but is not helping much with the new box. The smell that is coming out is definitely a poop smell although we did end up with a pee smell once but I believe the litter was just over saturated with it and we haven't smelled the pee in about a week. The poop smell continues. I believe part of the problem are the holes on the step up to the globe. They allow odor to seep through them from the drawer. I know that some people have over the holes up and I was wondering what they were using to cover them?

I have tried using Ammo Carb which seemed to decrease the smell greatly but it was still there and unfortunately it only covered the smell for two days. I only used the Ammo carb in the drawer, in the liner. Should I also put it in the drawer itself. I hesitate to put it in the litter but if that has worked for people I would like to know. I'm also concered that I did not put enough of it in. I probably put about 1 to 2 cups in the drawer. Should I be putting more in?

I want to eliminate the smell not add air fresheners and so forth to the air because they often cause me to have headaches and I'm worried that one of my cats won't take to the smell and will choose to do her business elsewhere. Any other solutions are welcome. I really like a lot of things about the Litter Robot so I want it to work out. Thanks in advance.

I am currently using Ultra Pearls and I am happy with the reduction of the odors. When I first had
the LR, I was using Cat Attract litter and it really smelled bad after a couple of days. Cat Ammo
worked somewhat, but I put about 2" of Mimi crystals litter in the drawer (much cheaper than
Ultra Pearls) and this elminates the odors and continues drying anything dropped in the drawer.
Like the Ultra I change the Mimi when it starts to change color.