They do smoke on boost especially when using normal fuel, they run a lot cleaner on V-Power/Premium Diesels. I used to run on cheapest i could find ie supermarkets and they just coke up and smoke there **** off the lag was unbearable. If i haven't booted it for a while it will still smoke a little when coming on boost. In regards to the point on which it boosts, mine boosts at 2k<. The joys of TDi's!