Better to get the airbox on first, else you could find the new maf dies just as fast. I'd also recommend buying a new maf, you don't know that a scrapyard job isn't already knackered or well on it's way. Make sure you buy genuine too, siemens vdo, is available from most motor factors.
I think i have a standard airbox kicking about somewhere, in fact...
I think i have a standard airbox kicking about somewhere, in fact...