I know this is an old thread but i though i would add my 10 cents worth as i came across this thread while trying to figue out this issue in my same car i disregaded this thread because no one here seemed to really get it, so anyway its 2017 i just installed new injectors higher rating ones into a VS commodore which has got a performance chip in it, i put in higher flowing injectors 250CC where the standard was 208CC in a VS commodore ecotec V6 The VZ commodore have the same 3.8 litre ecotec, so i ran into problems with the first install i thought at first the rough idle poor starting was a relearn issue, i then got hold of the guy who sold me injectors, he wanted to clean them etc... i said pretty rare its the injectors, anyway i pulled the injectors out a second time , and the end seating caps had come off fallen into the motor so , not to worry (well for a minute) until i researched what to do next, well these seats burn off apparantly if you lose them inside the combustion chamber i lost 5 of them, this time I threw some oil around the new O-RING seals when re-installing these injectors, and gently put the rails back in this time and found out also those seats you push on the end are not really neccesary I thought they protect the jets from gum but apparantly the revised injectors they are not neccesary on talking to the kind gentleman who sold them to me on EBAY . They are bosch aftermaket performance 250 CC injectors anyway i was also getting a slow start, so what happened to your VZ i can tell you, you did not put oil around the seals or the seals were not sealing as they should, i replaced the seals with thicker seals that came in this seal kit which seemed to be different put the injectors back on , and no more problems, it has to do with the job you have done installing them you must be very gentle with these injectors when putting them in gently pushing the fuel rails in place evenly otherwise you will get a minute amount of air whistling in through the seals, i hope i helped you all here, there would have been nothing wrong with the original injectors you bought, like i said i have fitted higher flowing injectors 250 CC injectors car now starts beutifully way more responsive no retune needed, your welcome everyone,
and finally you redid these injectors a second time but you still did not get it right and i am thinking dont take this personal you were heavy handed and rushing quickly to get this done, now the second time you say you were still getting a slow start which means you did not quite do it right the second time as well, i was getting slow starts and rough idle, but i researched hard and re-did the injectors again a second time and now the VS (same motor runs beutifull even with higher flowing injectors)
