Burton boots run on the narrower side of things from what i hear (and experienced with my own boots). The pain/pins and needles sounds like it is an issue with the width, which is similar to the problem i had with my Ambushes recently (only happened on the slope, when strapped in etc). If you have this problem around the house it will only get worse on the slope.
As for sizing, i was always under the impression that the half sizes in shoes were always the same length but a bit more width. So getting the 9 might have exacerbated the narrowness problem.
For me, i took the following steps and they are now starting to feel much better:
1. Took out the inner sole for a tad more space inside
2. lower section not tightened at all
3. Hair dryer for 3-4 minutes then quickly put the boots on and try to mold them (5 stomps on the heel then 5 stomps straight up/down)
4. Used business socks instead of sports socks
They are moldable according to burton customer service, and in my opinion that step helped. After 4 - 5 days riding, i have returned the inner sole and started doing slight tightening on the lower section. A few more days and i will start using normal socks i think.