Just bought a used kel-tec p11

Sorry for the late reply but you would have to make me crawl back under the basement steps and feel around among the spider webs and other creepy crawlies.

The warning regarding ammunition in my manual is in the paragraph corresponding to the ammunition suggestions in the current manual. My manual does not have the line about the pistol's "extended service life" and in its place is the ammunition warning. My memory is a little faulty as this actually warns against frequent use of +P ammunition and I have an annotation at the end of the manual regarding the use of heavier bullet weights by the original owner along with a receipt for a new pistol. There is also a recommendation to not use 180 gr bullets with the 40 S&W in the manual. I guess that confusing the two manuals with each other is how I came about the idea that one shouldn't run heavier than 115 gr, maybe 124, bullets in the gun.
My Kel-Tec has a slightly higher serial number than yours so I'm guessing the online manual is for a newer model that may have had some design or material changes since mine was made. Either that or the online manual is the older one with mine being a newer update which I think unlikely. As there seems to be a difference, I would contact Kel-Tec and ask them for an opinion. It may also be that there have been changes in ammunition which make the advisory in my manual obsolete. In any case, I'll stick with the 115 gr bullets as I feel the higher velocity is more likely to cause the bullet to have some amount of expansion which I feel is desirable for best effect.