I just picked up a tt automatic engine local from a guy. He told me it runs great. I brought it home & put it on the stand. It appears to be a rebuilt engine it has the round metal void if removed tags on the freeze plugs. My question is I was checking the resistance on the injectors & noticed they are red top. Are those NA injectors? My original injectors are blue/gray looking. I was wondering if there is a way to find out if this is a true TT motor & a way to find out what year it is.