Range rover 4.6

Hi , new to this forum and hoping to get some answers from proper guys who know the old m reg 4.6 model which i have bother with.
it is running very rough on what should be tick over and backfires a little when pushing the the throttle and cuts out.had a new coil pack fitted, new plugs . compression test is good fuel pressure is good,cam and crank sensors are good. it seems like its not firing on all cylinders but spark is huge.
can the timing chain slip a tooth on these?
HELP AS I WANT TO LOVE THIS CAR AS ITS MY FIRST

CHEERS ROB

Post in the range rover section pal, the cleverer people than me will help, I got a diesel rr so not sure on the petrol model

It sounds like it could be the mass airflow meter giving up the ghost.