2015. From what I can remember, since it's been so long and I've replaced so much. I live in New England. The Z sits pretty much November - March. I don't run the car when it's in the garage for the winter. This happened that March/April, it wasn't as severe the car would start up after a few turns of the crank. Now it's still been pretty cold up here. I had a set of 555 old styles on the car with the issue and swapped to the 615's to try and fix it. I bought the injectors from Bernie. I believe they are refurbed.