Unfortunately, CT has a 15 year statute of limitations for collection of property taxes (such as these vehicle taxes: https://www.cga.ct.gov/2008/rpt/2008-R-0643.htm). This means that if your taxes were due 14 years ago, they are within the proper time limit to enforce them now. (While I doubt it is of great consolation, you are not alone, and there are several news stories of other citizens in your state that are facing similar enforcement actions).
You can try negotiating a lower payment amount with the City, they may be willing to do so, but they have little incentive to agree to a lessened payment with you.
Some general debt negotiation considerations that you can use include:
When trying to settle a debt, creditors generally prefer lump sums over payment plans. They are often willing to accept an amount less than the full debt (the trade off is that they get a quick payment and don't have to worry about ongoing collection costs or administration). If you do not have the ability to offer a lump sum for something the creditor will accept (some will accept a small portion, while others want close to the full amount), you can try a payment plan, these are less satisfactory to the creditor (especially if they have a lien on your property already), but if you are willing to offer something with a reasonable chance to get the creditor a large amount of their debt back, you are likely to get them to accept it.
Whenever working with a creditor, make sure that you keep your communications in writing (if you speak to someone by phone, promptly send a confirmation letter to summarize your conversation), as this will help to ensure that there is no confusion later on, and you will be able to enforce your settlement against any future collection efforts.