You can read my experience and many other people's experience with going from a pure hot air to cold air intake on a naturally aspirated volvo 850 here. This is a very common fix on older volvos.
http://www.matthewsvolvosite.com/for...php?f=1&t=8830
In short switching from hot to cold air intake on a volvo is universally accepted as a quick and easy way to improve both fuel economy and power. It has been tested many times over.