Test drive 1989 si prelude

I took a test drive near by my place selling the prelude si for $1,300 b20 engine.salvage tittle no pink slips
when I press on the accelerator its kinda have a jerking/hesitation motion like it wont go fast,then I realize have to accelerate slowly to the pedal, to go faster.
is there something wrong with the fuel filter? or other parts?
stage 3 clucth,40kmles on the motor,220 kmiles on the chassie,with headers,and whistling sounds comming from the plenium's sensor.

Bump!