8 year old cat chronic mouth sores, bad odor, vet pulled teeth already

Question
I have an 8 yr old cat who for the past couple of years has had chronic bad breath and about a year ago I noticed she wasn't eating and had mouth sores. After treating her in various ways the vet said we should pull her teeth and it would all go away; he pulled them and about a month later the problem returned. She has been tested for diabetes, FIV, leukemia etc and her kidneys are healthy. The vet has told me to bring her in for steroid shots...which I've done a couple times but each time the problem just returned within 2 months. The vet thinks its an allergy to foods we tried zd pet food brands but she wouldn't eat it. Is there a good pet food thats not outrageously expensive? Is there an alternative treatment, supplement for her problem? I've read about enzyme supplements, vitamin supplements etc but I'm confused where to start. She also has EXTREMELY bad smelling bowel movements...they have always been strong but are MUCH worse the past few months. Right now she's lethargic, not eating, yelps when she even licks food and her coat is oily & dirty looking. I am so worried about her to the point that I start crying when I think of the pain she's in as well as how hungry she must be...please give me any help you can anything will be greatly appreciated. Thank you

Answer
Oh Angie, Yes, I would be glad to help your girl...POOR kid.
Ok, let's get a good wet food into her and some supplements.

First, can you buy some Innova CAT food ( wet) or WEllness CAT / canned???  YOU can find them at the local pet store.
Make sure she gets 3 meals per day - Just take a regular can and make 3 meals out of it.
Add a teaspoon of water to the food - to make it even softer.
YOU can also buy the paste for pets that won't eat.  
Do you know what I mean?  If not , I will try to find you a link to the special paste for calories...

Next, I would like to try her on the NuVET Plus - get the dog powder not the cat powder.... The DOG powder tastes better and CATS love it.
Go here and order the NuVET Powder / ASK for the 30 count of powder - tell them you want the Canine one.
Give her 1/2 a dosage per day for the powder / mixed into the wet food.
This is an Immune system booster and Allergy blaster...
1-800-474-7044
http://www.nuvet.com/81098
Tell them Marie sent you : Marie Peppers of Ask the Pet Nurse at All Experts...

We can try a few other items - some oils and vitamin E.
Let's try the new food and the NuVET first.
OK???

BEST wishes

Marie Peppers LPN MA