Thanks for the tips on leak checking - I reckon my workshop guy will be on to it.

ademon - My engine only makes 370 with the LD340 so its not crazy on the cam side.

Re the intake - it was new so its not milled.

This is why I find it so hard to believe its leaking - it was a flush fit using if Felpro gaskets.

What makes e think you're both right is that the AF gauge goes off the scale lean when I lift off.

Probably sucking air in no doubt.