My fiorino judders at 2000 rpm in 5th at around 50mph - any ideas?

Hi
This has been an issue that we are trying to get to the bottom of
I have posted about this problem on here in the fiorino section under mass airflow sensor)
I tunk I've solved my issue buy ditching the current air box engine cover and fitting a cone filter
My was 2000rpm at around 40mph, this seems to a ecu problem as if the engine is starved of fuel and goes away when you give the engine a little more gas or change down to 4th
Anyway so far I've cured mine
Have a look at the conversion under Engine cover one,two,three
Luigi