ok so it seems since i have fitted the pd160 intake and the green cotton that i get a low idle, is this something everyone has

im assuming it would be down to the air fuel mixture being altered so that the car now runs with more air than fuel and therefore the car runs leaner...causing lower idle?

or is my petrol based air fuel ratio calculations not relevant with the diesel

Is the MAF Sensor connected back on properly and the relevant connecting hoses? if not put the standard box back in to see if it sorts the lumpy idle, if it is the same with the standard box then its most likely the MAF.

Also could be fuel filter clogged not giving enough fuel to match the air coming in it may need replacing.

Is the MAF Sensor connected back on properly and the relevant connecting hoses? if not put the standard box back in to see if it sorts the lumpy idle, if it is the same with the standard box then its most likely the MAF.

Also could be fuel filter clogged not giving enough fuel to match the air coming in it may need replacing.

Diesels run in "lean burn" mode at all times except sometimes when the throttle setting is high and the revs are low (and then they over-fuel and black smoke), so increasing peak airflow will make no difference to idle, which is totally dependant on fuel supply.

Fuelling problems from a clogged fuel filter are most likely at high throttle, and should just manifest as a lack of power. So I'd do the usual "disconnect MAF" test, and then start wondering about testing the idle stabilisation circuit.