Thanks for the advice. The previous owner fitted the wrong air filter
and only fitted two of three nuts retaining the air filter box lid.
Correct Part No: 60623350 282mm long
Incorrect Part No: 60603977 258mm long for 2.0 engines
It must have been flapping around in the air filter box like the proverbial "P**** in a shirt sleeve". The box was full of leaves and the MAF grill clogged.
I sealed the hole in the middle at the bottom of the air filter box by sandwiching it between a 6mm bolt head & washer and washer & nut. This hole looks like it was produced in production and there must be a reason for it ... can anyone enlighten
However, without sealing it would have allowed unfiltered air to mix with filtered air passing up through the middle of the air filter. The small hole 3 mm approx at the outer edge is a water drain hole. Any air coming in through this hole would have to pass through the air filter.
I gave the MAF a good clean with contact cleaner and cleared the clogged grill, carefully.
Now the good bit. I took it for a test drive
Like the proverbial "S*** of a shovel". I redlined it without a hint of hesitation. I now know what all the fuss is about with this engine. What a beast!
One happy bunny