2006 XC70 MAF code with issues

[abscate]

Total speculation on my part but I'll guess that the throttle position in "over run" is not the same as idle. Fuel can be nearly shut off and extra air can be let in to quench CO, with no load NOX won't be high, so the car will run clean

Yes, I did make that all up in my head.

[terryfil]

I've been through this. Sounds like your mechanic is just following the recommended actions displayed on his diagnostic tool. I don't think that's going to do it in this case. He needs to dive deeper - which involves watching and understanding live data, and probably a smoke test. Quite a few mechanics will be in over their heads on modern vehicles when you bring them something with a little funky going on.

MAF code and rough running at various times but more often just after startup when hot. Gaskets tend to leak more when cold, so that's probably down on the list.

An intermittent bad reading from the coolant temp sensor can cause this. A air charge/temp sensor might do it too. It's not on the manifold on these cars. It's a combination air pressure and temp sensor. Technically not a MAP as it's before the throttle plate, not after.

Because I've had problems with this on my '06, and it could cause your symptoms, I'll mention:
Have your mech check the throttle body. He'll need to record live data during one of those rough starts. Also observe how the throttle plate position acts while driving. Throttle plate position (as reported by the TPS) should be no higher than around 7% open during hot idle in park. While driving you slowly press and release the accelerator pedal and look for spots where the throttle plate appears to be sticking.
In my experience a sweep test with the engine off looks like there's nothing wrong with it. You have to perform functional tests while the car is starting/idling/rolling down the road.

The ECU command output to the throttle body isn't necessarily linear to torque request (accelerator pedal), but most of the funnier stuff the ECU does in this regard happens with quick changes on the accelerator pedal and during hard acceleration to moderate hard gear shifts. On a longer 10-15 second sweep between foot off and about half way down on the pedal and vice versa you should see a smooth predictable correlation between the two.

If any of the above turns up nothing you probably have a air leak and just aren't finding it. Could be almost anywhere including PCV, power brake system, vacuum check valves, or even the evap system, hoses, purge solenoids etc. Hence a smoke test might actually be the faster way to find and remedy.

I'm having a similar issue with an '06. Threw MAF, fuel trim and O2 codes. Another shop replaced the MAF, no change. I replaced plugs (It was due) and fuel filter, cleaned TB and no change. When I had the TB off, I didn't pop the cover and check the gears though. I'll take it off again and check. From everything I'm reading, it seem that it's the TB. What else can I check? Fuel pressure's good at 58-60PSI and I can't tell if the throttle plate is hanging up with my scan tool, it seems smooth, but commanded and actual angle seems all over the place on these