to me it looks like a lip would give you very minimal effect, have you lowered your sentra? lowering her will decrease wind going under the body, and a front sway would help keep her nose down/stiff in turns. motor mounts will help with wheel hop.
talking body kits, most don't actually have much down force on the nose, the weight of the engine usually keeps a car's nose down, most full racing kits just fill the space between the front bumper and the street. it usually increases wind resistance(very little), but decrease lift from air under the body.
it will be hard to add something that wouldn't dramatically change the front end, but actually give you real down force on your nose...