Suucces! I turned off Ajax checking, disabled joomlatools loading in layout, and installed a new plugin from
www.kinesphere.fr
to disable core loading of joomla. That stopped mootools loading in the print preview window too. Then I deleted all lighbox, thinbox, etc. The final culprit was Google: it asked me to dad a meta 'verify' directive for site map checking, which somewhow was getting mootools loaded. Also the Google translation plugins installed mootools. Then I added my own scripts for popups which are <1KB.
The only thing I haven't got working is the core rating system. Eventually I'd like to add lightbox and so on back in, as options for registered users.
Thanks for the help