Chainsaws....love 'em....hate 'em!!! I personally do not like them, I think i is a cheesy scare and it costs me a lot of money each year in broken chainsaws.
However... you do need to be responsive to your audience, and like it or not they LOVE the chainsaw!! IF you don't think so,, run a chainsaw for a few groups and watch their reaction. Then skip a couple groups NOT using the chainsaw.
People will have a great time in your attraction, the chainsaw is not realy a surprise (they have been listening to it for two hours in line) but if it misfires and they don't get the saw they want their money back!!!
I looked into the sound chip ones, but my actors break several REAL chainsaws, they would destroy the electronic one in less than an hour!!!