The fluttering has two possible causes - you have crap gauges (if they have restrictor clamps in line with the hoses then this is probably the case, like these):
http://www.busters-accessories.co.uk...EVG2&kw=vacuum
or it's runnning lean. If it' is running lean, you need to upjet of course but if you take the appendix thing off the left side of the airbox and plug all the holes, you can get to the balance adjuster while the airbox is attached.