Hey mate,
Does it sound anything like this... http://www.navara.asia/d22-engine/7344-loud-turbo-whistle-inside-cab-wtf.html
If it is, check that you haven't lost one of the bolts from where the dump pipe meets the turbo
I've got 4 of em on my rear bar. They do the job. I only use them to light up stuff close in front and to the sides but. Then got my big spotties on the bullbar for lighting up WAY out front.
I think this post was meant to have pics. Would be nice to get ahold of them if there is any.
http://www.navara.asia/diy-modifications-build-ups/1282-diy-roof-console.html