It does sound like a boost leak, rubber hose come off somewhere or a large hole in one?
I had a mega hole in my Freelander turbo diesel intercooler hose and the jeep wouldnt hit boost or accelerate well, was very lumpy and chucked out pure black smoke. Changed the hose and it was fixed, easy!
Press and feel all the intercooler hoses there may be a hole or tear that you can only find by touch rather than by sight. Sounds like you get enough boost pressure for one light then the hole opens and the air gets sucked in losing you boost pressure.
Worth a check anyway.
(and I would edit your 2nd post re when it happened, unless you were on a private road / drag strip etc, just a heads up )