I have the car back now.
Turns out that the wastegate plumbing was wrong, and has been that way since I got the car 6 years ago!
The adjustable boost controller was installed inline in the hose running from the bottom of the wastegate to the intercooler. The top of the wastegate was vented to atmosphere.
The mechanic re-plumbed the lines:
- Bottom of wastegate -> intercooler
- Top of wastegate -> Boost controller -> T-fitting (which he added) where boost sginal comes from
Car seems to come on boost sooner, but I haven't had a chance to really try it out. It's 41C (106F) with the humidity here today, so I'll wait until it cools down.
On the highway home I didn't feel any hesitation/stuttering as boost came on, but no WOT blasts yet.
Still not sure why I was seeing smoke??
I don't believe he checked the fuel pressures, but he seemed happy with how it started, idled and drove.