I'm working on a 30 year old car that, when tuned properly, doesn't emit any more carbons than a car just off the line last month.
I doubt that, unless you put in a new motor too, at least if you compare it to a modern car with similar horsepower and weight. Automobile technology has improved a lot in the last 30 years - why wouldn't it? Even something as simple as bicycles are built much differently these days than they were a couple decades ago.