The Invector Plus choke tubes were first introduced in the 1989 Browning Catalog which was published in October 1988. Keep in mind that the Invector was already standard on most shotguns and the Invector Plus was slowing being made available to many models. The Invector Plus choke tube system was available first on BT-99 models and then the BPS and high grade doubles.
I don't think there is an invector plus model. Invector Plus is the choke system Browning uses on newer shotguns.
You will have to call Browning to find out.
Made in 1996
Yes, all Browning Invector and invector plus barrels can shoot steel shot.
Best bet is to have it examined by a good gunsmith.
Look at the choke tubes.
Send it to a Browning authorized repair center.
Ask a gunsmith for help
Yes, in the new A5.
If you don't have a manual, request one from Browning. If you can't wait, find a good gunmsith
This project should be probable.I would have a competent gunsmith give you a quote for threading the barrel to except the Invector plus choke system.
Its about $550 @ basspro