Accord 2.2 diesel tourer 2005 - runs fine without airfilter, but dreadful with..
 

My 2005 Tourer 2.2 developed a fault while driving, lost all power as if the turbo had failed, and the glow plug light kept intermittently flashing.
ODB said P1237 lack of boost?Anyway my decent local garge plugged in their fancy ODB and said it seems like air mass flow sensor, which was a cheap and easy replacement, and a new air filter.
The car now drives better, but seems to hit a wall at 3k, however with the air filter out it will rev all the way to the redline. It is not giving any fault codes now. Any ideas? Same problem with old filter too.
Tried all pipes, no leaks, splits or fit issues.
We have replaced air mass flow sensor, map sensor, cleaned egr, checked intercooler, turbo. its wierd.
Take out air filter it runs like a dream. Anything else other than chucking it off a cliff?

Does your scanner read live engine data? If yes, look at the long and short term fuel trims to see if the engine computer is reading a lean or rich condition.

Did you use a Honda or aftermarket replacement mass air flow sensor?

Ok, I'll do that, does rich or lean apply in diesel engines though?
Aftermarket, but still made by bosch like the honda one.

Forgot you had a diesel. The fuel trims should still apply to a diesel engine.engine. Look at the fuel trims at idle and when you increase rpm when the engine struggles.