people say not tuneable but theres everything out there like cams and verniers, throttle bodys, manifolds, induction kits, gasflow the head. you'd have to spend over 1k on a zetec to get 150 bhp, and i've had 3 rs2000, i've got 2 mates thats had 1 a piece and not 1 problem, and i've never heard of the head cracking. maybe put some water in and this wouldnt happen.