It was running Rough, it wouldn't idle but would hunt between 550 to 1200 rpm
noticable lack of power (more so at low revs).
This was one of the last checks I did after replacing the sparkplugs, checking the MAP sensor, checking the MAF sensor, checking each coil pack, checking the fuel pressure in the line, looking into the EGR system, checking for water in the oil, checking for oil in the water ect...
Put it this way, it didn't seem like a compression issue but I was running out of other things it could be.