This has become quite an epidemic so figured its definitely worthy of a sticky
The following vendors are VERIFIED to sell knock off fake china made siemens deka injectors:
TrePerformance
FIC
Amazon
eBay
The siemens deka line of injectors are the most copied injectors on the market. Unfortunately there is no possible way to verify them visually since the knock offs use actual genuine siemens deka housings. Only way to know is to cut them open and inspect the internals. The really cheap knock offs can be identified by the part number being in the wrong location and a casting bump where it doesnt belong.
As is typical with most knock offs they usually have extremely poor and intolerable transient fuel delays that cannot be mistaken. The better knock offs do not usually have this issue as pronounced but do still have inconsistent fueling usually just off idle. All genuine siemens deka injectors are flow tested during production and must be within' 3% of published data otherwise siemens does not sell them. If fueling is inconsistent by more than 3% during a stable condition or at WOT then you are guaranteed to have knock off injectors.
There are only two vendors in the US for siemens deka injectors that I know of. Poweraddersolutions (CDL Ent) and another on the west coast. If anyone knows of another genuine vendor please do post here.