[uh-oh]

a couple things could be doing it

1. the tempo of the beat/project. Fl studio's default tempo is 140 beats per minute. bpm. fl studio was originally intended for like techno/electric type music, most forms of music dont get that quick, so if you sample a soul song, chances are its original tempo might be like half that. 70 bpm. so really unless you match the tempo of the project it will always sound somewhat sped up, i try and at least bring it in the 80's range. quintessential hip hop is around 93 bpm.

2. you might have chopped wrong. you might think you have a 1 bar chop, but in reality it might be 1 and a half, or 1 bar and 1 beat. it might be a little longer than you thought, so when you time stretch it to 1 bar, you are condensing more than 1 bar of music to play as if it is 1 bar, this will speed it up. the best way to find out if you chopped too much/have a little extra is to put drums out over it and see if they line up right and it sounds like it should.