^ celerys right
unless your ported, running a 3.8TB, w/ open exhaust and or cam'd - the SPI MAF houseing is adequate
Im ported, running a 3.8TB, and went up to a late model 3.8 MAF houseing w/ a 3L MAF sensor. We're talking a 4" MAF houseing. Im considering dremeling the sample tube to match the 2L MAF and drop back down to the 2L sensor - not sure yet. mid range to top end the 3L sensor is sweet, bottom end it can be a dog if not driven right.
an alternative I toyed around with is swapping in a 5L MAF sensor into the 2L houseing - its very intruigeing what the results were, I ran like that for about a year. <--- try this .... you'd never believe it if I told you my results (and before anyone chimes in, I never ran rich or lean with this setup)
I did find that the 4L and 3.8L sensors dont work very well in either houseing.
the 3.8L MAF setup is viewable in the link in my sig. Let me add, it requires a 4" MAF adapter to run this setup aswell as a 4"/3" coupler.