Hi vti - Warm up buggy fully first. Go for a good blast to clear everything out, then bring it in and pinch fuel line straight away. Adjust as needed, then go for another short blast and test it again until you get it right.
I´m certainly no expert, but I was taught this method by a couple of racers I know who are very experianced tuners. They combine this method with the clean take off method as a confirming test to ensure correct LSN setting.
The lean bog - yeah ?? Most of the lean bog problems with the long lsn carbs was solved by setting the needles like I described at the bottom of my previous post (check that , as I added a couple of things as an edit).

Chipo, set the idle gap like vti suggests. Maybe tune everything in with the original 8mm insert, then place your restrictor in when it´s all running good, then fine tune from there. It really does sound like an idle gap thing upsetting your tuning.