one of the DVDs out there has a trivia track in which it points out the differences between what you see and the actual script along with other bits of info. Like with the "let's run some red lights" they did a number of different lines, the script for Weaver was supposed to have been "used car salesman"
Yeah, that was it. "Used car salesman".
Its a shame they cut the dialog about the nerve-gas, which is hilarious. But I suspect it would have taken the punch out of Venkman's line, so that might be why they cut it.