Hiya Scooter
I'm not sure you have done something wrong; as you say it is a fairly straightforward job.
There have been some recent threads on poor performance from new chinese clone injectors purchased from ebay as opposed to the the OEM Bosch style. You may want to search to see what you find.
I expect that the injectors either aren't spraying fuel correctly or at worst case not be seated correctly.
Do you have access to a scan tool to look at the live data? If so that is worth hooking up and have someone monitor it when you decelerate.
It would be worth taking the injectors to have them bench tested to see if they are working properly. If you want to do it yourself see this video. This is base level testing - if you search there are some higher tech home solutions that you could build.
For me - I'd take them to a fuel injector specialist and have them bench test them for me.
A full DIY diagnostic proceedure is shown in this video; however, from the description of the problem I'm not sure if you would pick up the issue at idle.
I trust this points you in the right direction.
Cheer n Beers
Jolls
