The Syntace stems had a fault that saw them crack, do you know if those are OK?
They had a recall on F99 stems several (at least 3) years ago. I bought a used stem on ebay around then, or maybe even 4 years ago. I looked at the recall info on their website, and saw my stem was affected (based on some identifying number - date?? on the stem). Anyway, I contacted them, and they replaced the stem immediately with no questions asked. Didn't ask if I was original owner or anything. All I had to do (based on their emailed instructions) was to cut the stem and email them a photo that showed the batch (or whatever) number and that it was cut.
There's been no problems with Syntace stems that I've read about since then. I'm very happy with mine for what it's worth. It's right around 100 grams for a 105mm stem with the standard bolts. I think you could lose another 5 or 10 grams with ti bolts (which I had and kept from the original stem!), but I happen to think the black ones look better (a travesty on ww I know!). They are a very large bang/buck ratio.