Help, I spent the weekend cleaning my Boost sensor and my ERG valve on my 04 120cdti vectra after reading some of the posts on the site. I also did the mod to remove the airbox baffle. My fuel economy has shot up, even reading 57 mpg on the motorway when I was cruising at 70. After about 300 mile or so, my spanner light started to come on and off. Now it's on permenantly. I have no loss of power or performance and my fuel consumption for a 230 mile journey today was 54.4 mpg; the best I have ever seen for mixed driving. I have reversed the air box mod to see if it was the cause but no. Any ideas please?
ps I noticed that my criuse control is being knocked off every time the spanner appears. As it's on permenantly now the cruise is working again.

Ideas please