seconds, once you get back on throttle, I don't really see that the air 'dumped' will increase the volume of air that may already be in the airbox - you know what I mean? For instance, say you have an open intake like an Evo or something(I know they're not "better" than stock, but for example) and you dump the air back in to be "metered", its now in the engine bay for the most part - the sensor isn't measuring air going backwards through the MAF, so I still don't think it matters...

2001 MTM STG4 S4
2004 MB E55 AMG
AIM:zapco98