Older kitten w diarrhea returning?

My boy is almost 8 months old, and he was treated for giardia in January that he had had, but his adoption center and the vet hadn't picked up on since essentially November when he was adopted. His diarrhea from this mostly went away, it took a bit for the mucous to go away from his poo.

But, after a few weeks he started to get diarrhea again. It's not constant, like it had been. He'll have a bad poop and then some regular ones, usuallygoing a few days in between bad poops. His mood isn't affected at all, he eats plenty.

This morning, he had one very healthy normal poop, then half an hour later, a messy one. Odd timing!

My vet has done the big $40 "axial" or three-way test on him before, which only found giardia. They are sort of trying to get me to do that, but is that a waste of money since it's thorough and very specific? Could this be worms that lingered? Any advice for this situation in general?

There is a lot of good advice in an earlier thread here, http://www.thecatsite.com/t/248314/cant-get-rid-of-parasites-giardia.

Personally I had good results in curing persistent diarrhea in some feral kittens using the probiotic Saccharomyces boulardii added to their food.  It took about three weeks but then the diarrhea totally went away.  They were tested negative for everything that normal tests pick up, but both Giardia and Coccidia do not always show up on tests or smears, and these guys were too feral to be handled for medication.  I used the Nutricology brand S. boulardii (that does not have MOS in it) which I purchased online and I mixed it in with their wet food.  If the diarrhea came back, I would put them on it again.  I can't say for certain it cured giardia because it was never diagnosed, but it DID cure diarrhea that had gone on for a couple of months.

I am in the same boat. My 5 month old kitten had an awful bout with Giardia shortly after adopting her a month ago. She had two rounds of flagyl and three rounds of panacur (last one administered by me), and still her bowel movements are not what I like (normal ones, then a bad one). She also will pass gas with a tiny bit of feces (I grab that with a tissue or baby wipe). Just sent off stool sample this week and it came back negative for Giardia or any other parasite normally screened. As far as food goes, she is getting kitten chow dry, Royal Canin GI vet rx canned food, with fortiflora and s. boulardi. I'm hoping it's just a matter of time now and she'll will outgrow it. I would have her screened for T.foetus but the testing is so invasive; I'm going to try to hold off until if and when she has full fledged diarrhea again. I am hoping it's just a gut thing and the probiotics will get everything back on track soon. I know kittens and puppies GI tracts are sensitive. I just really do not want the horrendous diarrhea to come back!