Peugeot 206 Exhaust Manifold Problems

Hi have changed the exhaust manifold gasket a couple of times,but it keeps blowing,nothing wrong with the manifold or head,and im tightening down from middle outwards gradually from left to right and right to left,im am not using any exhaus...

I have just replaced the exhaust manifold and put the old sensor back on and the car sounds better but the engine light has come on and stayed on how can I switch the light off

I have a 206 gti with a clicking noise when accelerating. checked the drive shafts and the noise seems to be in the gearbox diff has anyone had this problem.