exesive crankcase pressure with no exesive oil use would indicate a fault with one of the valves ,this coupled with rough running would suggest u need to get your tappets checked. not expensive.as for light .it will have come on due to above fault in a convoulted way.if im right then tight valves are causing faulty fueling which is detected by lambda sensor triggering fault code and light.
caine
July 2008