I have just exchanged the steering rack on me Vectra after blowing a hole in the seal?

After much headache and many wet pairs of trousers & undies I finally got it reembled, And the steering fluid level is holding at the correct mark all an annoying clunk has developed at the same time lurches in an slight upward motion and as far as I know all nuts/bolts track rods gear linkage and all engine anchor mounts are in & tightened to torque and what a job it is just to yank out the rack. Any way can any body enlighten me as to what could be potential causes in addition an engine management light accompanies the problem but I dont know if thereis any connection?