I suspect that "handling" has a specific meaning in vehicle parlance, so if it is a count noun then "a handling" is fine, but not if it is just an abstract noun. The rule is that the indefinite article "a" can only be used with count nouns.
However, I think that some count nouns that are used for some quantitative description have over time become abstract nouns. One example is shelf life, which in my sentence appears as an abstract noun. I presume that originally it was a count noun, which is why you must say "have a shelf life of N days". But although many people still say "have a longer shelf life", many others now drop the "a", for example "contributed to longer shelf life" in this article.
That said, there is also another factor that we must be careful to exclude from analysis, which is that articles, definite or indefinite, are very often dropped from titles and headings especially in news reports such as Mediterranean migrants crisis: EU to hold emergency summit.