Hi all I am not very savvy when it comes to cars so I wanted to turn to you all for some help before heading to a mechanic.

I have a 02 wrx all stock parts except an exhaust. During accelerating at low rmps the car seems to be "bogged down" then at 4500rmp's it jumps to life simmilar to Honda's VTEC. Is is possible the timing has fallen out of wack or something else? What are your thoughts? Thanks to all for your help.