Technical crazy fuel trim levels

[billynomates]

I have a 1.2 8v engine (2004)About every 20 miles or so I get a P300 code (multiple missfire)
I have replaced all the ignition, Co2 and MAF sensor, checked compression and am at a loss. The long term and short term fuel trim are all over the place! Today I got 47% positive short term and 0.5% negative long term. Yesterday was 5% negative short term and 52% negative long term! Other days I get both trims positive! Whats going on!!! This is sending me crazy! The car still drives ok albeit with a sometimes very rough idle.

 

[murfman53]

Any chance you might have a vacuum leak. Or, issues with fuel supply.

Considering you've replaced many items, and doing a compression test as well.

John.