need help with 1993 toyota trueno(levin) cam timing sensor (to exhaust manifiold

i did the exhaust manifold gasket and i had to take the cam timing sensor mounted on the side of the engine off,so i could get to the exhaust screw,lucky thing i had marked it, so by now i put my exhaust manifold gasket on and put the sensor back on,now the car is misfiring like hell...i adjusted it little by little and finallly it worked and got back to normal....now my mate has done exactly the same with his toyota trueno(levin)same year and shape but we cant get it to adjust properly,just wondering if thiers any trick to it,like engine at being at TDC or some thing else which will get the timing right for it to run properly and in his case the car wouldnt even start to run like mine had but ewas misfiring like hell,,,any help appreciated