Its your timing belt man, i dont know if it was you who installed it or whatever but whoever installed the timing belt probably missed a tooth or so, turn the crank until its a tdc, top dead center and the timing mark whould be at degrees or somewhere near that, if not take the timing belt off and set the cams to where the up mark is upm or if you have aftermarked adjustable cam gears to where the degree markings are up, and the carefully turn the crank to where the timing mark is at degrees and install the timing belt, make sure the you dont have to move the crank that much otherwise you might hit a valve.