Also check the vaccum pipe on rear of engine at the inlet manifold (under throttle body) Take pipe from throttle body to airbox off to see it !!
The rubber pipe/hose will have a metal jubilee type clip on it ... it bends to the right and connects to a metal pipe below the coilpack...
They are bad for going soft and splitting .... I just replaced mine on my 1.8 focus last night, car was running shite, rough lack in power, low idle and sometimes stalling etc etc, they also when soft colapse under throttle aswell (mine was both split and colapsed under throttle)
I got mine from ford parts for £12 posted (can give you part number if you wish)
If its your maf and you want a second hand one i was going to sell one as its working fine