I didn't see your earlier posts so I don't know the whole situation. Is your new kitten completely unvaccinated?
If this is the case, I do think you need to get the standard shots, barring the ones listed below (which are recommended depending on whether you intend to let your cat be indoor/outdoor etc.) and also you need to test the kitten for FELV and FIP even though you can't always tell about FIP.
The reason I think this is because I've seen lots of kittens come in from the wild or other shelters, and out of the blue they end up having some horrible disease. Even with paperwork there is no guarantee, but I can tell you, after a few close calls, it feels very reassuring knowing the kittens mixing with my beloved cats do not carry life threatening diseases.
This link does a good job of delineating the shots that are controversial or that should only be done in special circumstances:http://cats.about.com/library/weekly/aa080200c.htm
Here is an excerpt from the above article regarding sarcomas from vaccines and the recommended areas for giving shots and why:
"In addition, because of the risk of vaccine-related sarcoma, special vaccination site guidelines have been issued for all recommended vaccines:
Rabies: In the right rear leg
FeLV: Left rear leg
Panleukopenia, feline herpesvirus I, feline calicivirus (or 3-way): Right fore region (shoulder)
The reasoning behind this, unpleasant as it may sound, is that a VAS tumor on the leg can be treated by amputation, allowing cats can survive. Cats are wonderfully adaptive, and usually adjust quite quickly to navigating on three legs.
Fears about the possibility of vaccine-induced tumors have led many cat owners, particularly breeders, to refuse the FeLV vaccine for their cats. Presently there is no USDA standard for FeLV vaccines, therefore rating the effectiveness of the vaccines is difficult. Many veterinarians estimate the effectiveness to be between 75-85%, which lends some cat owners a reason to deny the vaccine. Personally, I'd rather risk the one in 1,000 chances of vaccine-related sarcoma against the 25% risk that the FeLV vaccination would not work. FeLV is such a deadly disease, so easily transmissable, that I would not want to put my cats' lives up against a statistical roulette wheel."