Powerbox - anyone try it

If it's what I think it is then you'd be better off paying the extra for a remap

Tuning boxes like these achieve results the simple and cheap way. You didn't provide a link and I'm too lazy to Google, but if you can, getting one that lets you turn it down is preferable.

Mine was half the price of a remap and more than half as effective; it spends most of its time providing just a little extra rather than the claimed 115 -> 140 bhp improvement. When it's at the default setting, it is true to the claims - big difference in performance, small difference in soot. Most useful in my case for towing.