Why don't you contact Matt P about two engines he has from two of these suggested vendors and ask him who they are from and the issues they have. There is more than one occasion from said vendors that issues arise but most feel its a waste of time to even post about it as they don't feel like causing a scene.
All companies have issues....no one company has a perfect record. Just because ppl don't post doesn't mean they had a great experience or a bad or experience. I have quite a few builds out there running and quite a few customers that have my parts on their engine as well as coated parts they've installed with no issue. Do they post about it?...no but that doesnt mean they are having issues. Please don't jump the gun on assumptions