There are some tuning boxes which do a reasonable job, but as has been pointed out they can be expensive. I've seen some priced at over £500, which really is ridiculous. That's the cost of 2 remaps!
As a cheap boost do a google serch for "Evry mod" and spend a couple of quid making your own tuning box. It'll be as good as the cheap tuning boxes off ebay etc. and you'll learn a bit about your car in the process. But I'd be spending a couple of hundred quid and getting a half decent remap if I was you.