The only results I hear about on this are problems. On a basically stock 99 4v a new TB and maf are worth pretty much nothing. Once you go with forced induction or have a ported/polished intake with all other bolt ons and have played with the runners a little, then you might see a small gain. Other than that, I have herd of a few people having problems getting the car to run correctly or randomly dying at stop lights after that swap.
I've heard several people say that they have dyno'd 10 to the wheels on this.....i have pretty much every bolt on except tb and maf...i need to update my profile
Yep, they probably do, but that has nothing to do with the mechanical difference from the stock unit. They are leaning out a/f ratio because it measures slightly different from stock. It leans out the mixture and basically just changes the tune. Which is why some people complain that the car dies when it's supposed to idle sometimes...like this guy(I started hearing this complaint over a year ago, just did a quick search and found this guy still having the same problem that others have fixed by going back to stock) : http://www.corral.net/forums/showthread.php?s=&threadid=498743&highlight=80mm
The stock maf is good up to almost 400rwhp. So if you really want to spend the money start thinking about a port/polish job on your intake. That has reliably given 10-15hp over stock or bolt on 4v setups.
But to each his own I guess. Good luck.