I wanted to get my wife's 850 ready for Winter. I replaced the cam belt and tensioners, serpentine belt and tensioner pulley (there was a shrieking bearing noise last Winter on freezing weather start up that went away 50 seconds so I changed them all out). After the timing belt was installed I spun the motor clockwise with a ratchet (2 times around please). Then before mounting the serpentine belt I started the engine to check the valve timing. Everything purred like new. I installed the serpentine belt and finished up. I installed a new fuel filter and changed the oil and filter. I wanted to take a run before my wife took it to work so we did. After about 45 miles we stopped and the car stalled. It started like normal and we continued to 60 miles. On the way home the car seemed to cut out every 15 miles as if the key was turned off. The Tach didn't drop, it was more of a stutter like a transmission... but definately felt uprupt like electric not fuel.
I happily took the car to my VOLVO specialist and he told me- Intermittent problem, no applicable codes, drive it until it does something I can fix.
There was a brittle purge valve hose that I replaced at his shop. I rode over to my friend's house and he happened to have an OBD II kit. I plugged it in and there weren't any codes. Then I unplugged it. Then I started the engine again and plugged it in. Then I unplugged it. Then I plugged it in again...

And the engine FLIPPED OUT!

Surging, black smoke. Code= overvoltage to air mass meter.

Local experts agree that plugging in and out the OBD II should never causes a spike and whack the electronics. (I feel like Columbus)

I think jacking that plug in and out damaged something. What was I thinking with that plug?

Coincidence?

VOLVO shop's spare AMM didn't correct problem when swapped.
The engine runs so poorly that I'd have to disconnect the AMM (go on get home mode) to drive any distance.
My VOLVO man has had the car 3 days (I'll bet his bill is approaching the value of the car) He only repairs VOLVO and is baffled and is looking at manifold leaks???@!!
I have a good idea it's ELECTRICAL!!!

Ideas???

Engine ran strong and temp norm 100 miles so I'm ruling out cam timing.

Hose to purge valve (just replaced) or electrical connector?
Big expensive brain box?
Any possible relation to running 20 seconds without alternator belt?

thanks
G