mine took a few starts to "relean" the sensor being there, but my blue car when I rebuilt the motor and started with the 4 wire on it it stuttered and died every time I slid it outta gear to come to a stop, so I had to adjust the air bypass screw so it wouldn't stinking die on me lol. check your TB air bypass screw, turn it all the way in, and if it dies on you just back it out a bit till it doesn't, now my blue car I'm talking about has a lighter crank in it so it dies REAL easy on down rev so it's very touchy.
you should see 1-2 mpg difference no matter how you drive it, if you drove it hard and got 28 driving it just as hard you should see 30ish.
the 4 wire TPS helps with the "low end loss" with a bigger exhaust too, I didn't have it and if I tried to step in it anything below 2,500 it puttered with the 4 wire it tries to pick up and go instead of falling on its face. all I know is driving with it and with out it, the 4 wire is pretty sweet for a "stock replacement" quick easy install and cheap!