om605 woes

[paranoid]

so just recently ive noticed my engine hunting, when it gets to roughly 60 c.possible hunting or even holding back 100-200 rpm.more noticable doing like 40 mph.wanting to nip it in the bud before it gets worse.fitted new plastic fuel lines under bonnet,got no .codes. seems ok clod and up to operating temps just the bit in the middle.any ideas please

 

[mioba]

when was fuel filter last changed.

 

[paranoid]

last year and put a fresh 1 on it today still the same

 

[carat 3.6]

Does it do it at idle? If so it could be the pump governor nut backing off slightly.