the DiffTech 200 mph shaft is a nice piece and will do what you want. you'll be surprised at the changes between stock and that one. one thing is you'll have to get used to "clanging" when loading and unloading the u-joints... just like an old muscle car. the feel is quite a bit different too. there's a mushiness that you don't notice until you change it out. the reason for the two piece has to do with critical speed. it's easier to get a higher one by having shorter pieces and with 2 you in effect have two shorter shafts. i had to do mine because of massive wheel hop at the track and snapped my stocker. i got mine right before they cam out with the 200 mph one. i'm limited to "only" 140-150 mph with my 3.91 gears
